Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

Directory of Open Access Journals (Sweden)

H. Y. Fu

2015-08-01

Full Text Available Observations of secondary radiation, stimulated electromagnetic emission (SEE, produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS and stimulated ion Bernstein scatter (SIBS in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

Emerging Carbon and Post-Carbon Nanomaterial Inks for Printed Electronics.

Science.gov (United States)

Secor, Ethan B; Hersam, Mark C

2015-02-19

Carbon and post-carbon nanomaterials present desirable electrical, optical, chemical, and mechanical attributes for printed electronics, offering low-cost, large-area functionality on flexible substrates. In this Perspective, recent developments in carbon nanomaterial inks are highlighted. Monodisperse semiconducting single-walled carbon nanotubes compatible with inkjet and aerosol jet printing are ideal channels for thin-film transistors, while inkjet, gravure, and screen-printable graphene-based inks are better-suited for electrodes and interconnects. Despite the high performance achieved in prototype devices, additional effort is required to address materials integration issues encountered in more complex systems. In this regard, post-carbon nanomaterial inks (e.g., electrically insulating boron nitride and optically active transition-metal dichalcogenides) present promising opportunities. Finally, emerging work to extend these nanomaterial inks to three-dimensional printing provides a path toward nonplanar devices. Overall, the superlative properties of these materials, coupled with versatile assembly by printing techniques, offer a powerful platform for next-generation printed electronics.

Electron irradiation-induced destruction of carbon nanotubes in electron microscopes

International Nuclear Information System (INIS)

Molhave, Kristian; Gudnason, Sven Bjarke; Pedersen, Anders Tegtmeier; Clausen, Casper Hyttel; Horsewell, Andy; Boggild, Peter

2007-01-01

Observations of carbon nanotubes under exposure to electron beam irradiation in standard transmission electron microscope (TEM) and scanning electron microscope (SEM) systems show that such treatment in some cases can cause severe damage of the nanotube structure, even at electron energies far below the approximate 100 keV threshold for knock-on damage displacing carbon atoms in the graphene structure. We find that the damage we observe in one TEM can be avoided by use of a cold finger. This and the morphology of the damage imply that water vapour, which is present as a background gas in many vacuum chambers, can damage the nanotube structure through electron beam-induced chemical reactions. Though, the dependence on the background gas makes these observations specific for the presently used systems, the results demonstrate the importance of careful assessment of the level of subtle structural damage that the individual electron microscope system can do to nanostructures during standard use

Electronic structure of multi-walled carbon fullerenes

International Nuclear Information System (INIS)

Doore, Keith; Cook, Matthew; Clausen, Eric; Lukashev, Pavel V; Kidd, Tim E; Stollenwerk, Andrew J

2017-01-01

Despite an enormous amount of research on carbon based nanostructures, relatively little is known about the electronic structure of multi-walled carbon fullerenes, also known as carbon onions. In part, this is due to the very high computational expense involved in estimating electronic structure of large molecules. At the same time, experimentally, the exact crystal structure of the carbon onion is usually unknown, and therefore one relies on qualitative arguments only. In this work we present the results of a computational study on a series of multi-walled fullerenes and compare their electronic structures to experimental data. Experimentally, the carbon onions were fabricated using ultrasonic agitation of isopropanol alcohol and deposited onto the surface of highly ordered pyrolytic graphite using a drop cast method. Scanning tunneling microscopy images indicate that the carbon onions produced using this technique are ellipsoidal with dimensions on the order of 10 nm. The majority of differential tunneling spectra acquired on individual carbon onions are similar to that of graphite with the addition of molecular-like peaks, indicating that these particles span the transition between molecules and bulk crystals. A smaller, yet sizable number exhibited a semiconducting gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels. These results are compared with the electronic structure of different carbon onion configurations calculated using first-principles. Similar to the experimental results, the majority of these configurations are metallic with a minority behaving as semiconductors. Analysis of the configurations investigated here reveals that each carbon onion exhibiting an energy band gap consisted only of non-metallic fullerene layers, indicating that the interlayer interaction is not significant enough to affect the total density of states in these structures. (paper)

Carbon nanotubes and graphene towards soft electronics

Science.gov (United States)

Chae, Sang Hoon; Lee, Young Hee

2014-04-01

Although silicon technology has been the main driving force for miniaturizing device dimensions to improve cost and performance, the current application of Si to soft electronics (flexible and stretchable electronics) is limited due to material rigidity. As a result, various prospective materials have been proposed to overcome the rigidity of conventional Si technology. In particular, nano-carbon materials such as carbon nanotubes (CNTs) and graphene are promising due to outstanding elastic properties as well as an excellent combination of electronic, optoelectronic, and thermal properties compared to conventional rigid silicon. The uniqueness of these nano-carbon materials has opened new possibilities for soft electronics, which is another technological trend in the market. This review covers the recent progress of soft electronics research based on CNTs and graphene. We discuss the strategies for soft electronics with nano-carbon materials and their preparation methods (growth and transfer techniques) to devices as well as the electrical characteristics of transparent conducting films (transparency and sheet resistance) and device performances in field effect transistor (FET) (structure, carrier type, on/off ratio, and mobility). In addition to discussing state of the art performance metrics, we also attempt to clarify trade-off issues and methods to control the trade-off on/off versus mobility). We further demonstrate accomplishments of the CNT network in flexible integrated circuits on plastic substrates that have attractive characteristics. A future research direction is also proposed to overcome current technological obstacles necessary to realize commercially feasible soft electronics.

Electron Transfer Strategies Regulate Carbonate Mineral and Micropore Formation.

Science.gov (United States)

Zeng, Zhirui; Tice, Michael M

2018-01-01

Some microbial carbonates are robust biosignatures due to their distinct morphologies and compositions. However, whether carbonates induced by microbial iron reduction have such features is unknown. Iron-reducing bacteria use various strategies to transfer electrons to iron oxide minerals (e.g., membrane-bound enzymes, soluble electron shuttles, nanowires, as well as different mechanisms for moving over or attaching to mineral surfaces). This diversity has the potential to create mineral biosignatures through manipulating the microenvironments in which carbonate precipitation occurs. We used Shewanella oneidensis MR-1, Geothrix fermentans, and Geobacter metallireducens GS-15, representing three different strategies, to reduce solid ferric hydroxide in order to evaluate their influence on carbonate and micropore formation (micro-size porosity in mineral rocks). Our results indicate that electron transfer strategies determined the morphology (rhombohedral, spherical, or long-chained) of precipitated calcium-rich siderite by controlling the level of carbonate saturation and the location of carbonate formation. Remarkably, electron transfer strategies also produced distinctive cell-shaped micropores in both carbonate and hydroxide minerals, thus producing suites of features that could potentially serve as biosignatures recording information about the sizes, shapes, and physiologies of iron-reducing organisms. Key Words: Microbial iron reduction-Micropore-Electron transfer strategies-Microbial carbonate. Astrobiology 18, 28-36.

New Insight into Carbon Nanotube Electronic Structure Selectivity

Energy Technology Data Exchange (ETDEWEB)

Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Jiang, Deen [ORNL

2009-01-01

The fundamental role of aryl diazonium salts for post synthesis selectivity of carbon nanotubes is investigated using extensive electronic structure calculations. The resulting understanding for diazonium salt based selective separation of conducting and semiconducting carbon nanotubes shows how the primary contributions come from the interplay between the intrinsic electronic structure of the carbon nanotubes and that of the anion of the salt. We demonstrate how the electronic transport properties change upon the formation of charge transfer complexes and upon their conversion into covalently attached functional groups. Our results are found to correlate well with experiments and provide for the first time an atomistic description for diazonium salt based chemical separation of carbon nanotubes

Carbon Nanotubes: Molecular Electronic Components

Science.gov (United States)

Srivastava, Deepak; Saini, Subhash; Menon, Madhu

1997-01-01

The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

International Nuclear Information System (INIS)

Tsukamoto, Sumiko; Murray, Andrew; Ankjaergaard, Christina; Jain, Mayank; Lapp, Torben

2010-01-01

A time-resolved optically stimulated exo-electron (TR-OSE) measurement system has been developed using a Photon Timer attached to a gas-flow semi-proportional pancake electron detector within a Risoe TL/OSL reader. The decay rate of the exo-electron emission after the stimulation pulse depends on the probability of (1) escape of electrons into the detector gas from the conduction band by overcoming the work function of the material and (2) thermalization of electrons in the conduction band, and subsequent re-trapping/recombination. Thus, we expect the exo-electron signal to reflect the instantaneous electron concentration in the conduction band. In this study, TR-OSE and time-resolved optically stimulated luminescence (TR-OSL) were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 0 C after beta irradiation and preheating to 280 0 C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination centre, rather than from residence time of an electron in the conduction band.

Carbon Nanotube Flexible and Stretchable Electronics.

Science.gov (United States)

Cai, Le; Wang, Chuan

2015-12-01

The low-cost and large-area manufacturing of flexible and stretchable electronics using printing processes could radically change people's perspectives on electronics and substantially expand the spectrum of potential applications. Examples range from personalized wearable electronics to large-area smart wallpapers and from interactive bio-inspired robots to implantable health/medical apparatus. Owing to its one-dimensional structure and superior electrical property, carbon nanotube is one of the most promising material platforms for flexible and stretchable electronics. Here in this paper, we review the recent progress in this field. Applications of single-wall carbon nanotube networks as channel semiconductor in flexible thin-film transistors and integrated circuits, as stretchable conductors in various sensors, and as channel material in stretchable transistors will be discussed. Lastly, state-of-the-art advancement on printing process, which is ideal for large-scale fabrication of flexible and stretchable electronics, will also be reviewed in detail.

Designing electronic anisotropy of three-dimensional carbon allotropes for the all-carbon device

Energy Technology Data Exchange (ETDEWEB)

Xu, Li-Chun, E-mail: xulichun@tyut.edu.cn; Song, Xian-Jiang; Yang, Zhi; Li, Xiu-Yan [College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024 (China); Wang, Ru-Zhi; Yan, Hui [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China)

2015-07-13

Extending two-dimensional (2D) graphene nanosheets to a three-dimensional (3D) network can enhance the design of all-carbon electronic devices. Based on the great diversity of carbon atomic bonding, we have constructed four superlattice-type carbon allotrope candidates, containing sp{sup 2}-bonding transport channels and sp{sup 3}-bonding insulating layers, using density functional theory. It was demonstrated through systematic simulations that the ultra-thin insulating layer with only three-atom thickness can switch off the tunneling transport and isolate the electronic connection between the adjacent graphene strips, and these alternating perpendicular strips also extend the electron road from 2D to 3D. Designing electronic anisotropy originates from the mutually perpendicular π bonds and the rare partial charge density of the corresponding carriers in insulating layers. Our results indicate the possibility of producing custom-designed 3D all-carbon devices with building blocks of graphene and diamond.

Electron Transfer Strategies Regulate Carbonate Mineral and Micropore Formation

Science.gov (United States)

Zeng, Zhirui; Tice, Michael M.

2018-01-01

Some microbial carbonates are robust biosignatures due to their distinct morphologies and compositions. However, whether carbonates induced by microbial iron reduction have such features is unknown. Iron-reducing bacteria use various strategies to transfer electrons to iron oxide minerals (e.g., membrane-bound enzymes, soluble electron shuttles, nanowires, as well as different mechanisms for moving over or attaching to mineral surfaces). This diversity has the potential to create mineral biosignatures through manipulating the microenvironments in which carbonate precipitation occurs. We used Shewanella oneidensis MR-1, Geothrix fermentans, and Geobacter metallireducens GS-15, representing three different strategies, to reduce solid ferric hydroxide in order to evaluate their influence on carbonate and micropore formation (micro-size porosity in mineral rocks). Our results indicate that electron transfer strategies determined the morphology (rhombohedral, spherical, or long-chained) of precipitated calcium-rich siderite by controlling the level of carbonate saturation and the location of carbonate formation. Remarkably, electron transfer strategies also produced distinctive cell-shaped micropores in both carbonate and hydroxide minerals, thus producing suites of features that could potentially serve as biosignatures recording information about the sizes, shapes, and physiologies of iron-reducing organisms.

Electronic properties of bromine-doped carbon nanotubes

CERN Document Server

Jhi, S H; Cohen, M L

2002-01-01

Intercalation of bromine molecules (Br2) into single-wall carbon nanotube (SWNT) ropes is studied using the ab initio pseudopotential density functional method. Electronic and vibrational properties of the SWNT and Br2 are studied for various bromine concentrations. A drastic change in the charge transfer, bromine stretching-mode, and bromine bond-length is observed when the bromine-bromine distance decreases. Calculated electronic structures show that, at high bromine concentrations, the bromine ppsigma level broadens due to the interbromine interaction. These states overlap with the electronic bands of the SWNT near the Fermi level which results in a substantial charge transfer from carbon to bromine.

Carbon Fiber Biocompatibility for Implants

Directory of Open Access Journals (Sweden)

Richard Petersen

2016-01-01

Full Text Available Carbon fibers have multiple potential advantages in developing high-strength biomaterials with a density close to bone for better stress transfer and electrical properties that enhance tissue formation. As a breakthrough example in biomaterials, a 1.5 mm diameter bisphenol-epoxy/carbon-fiber-reinforced composite rod was compared for two weeks in a rat tibia model with a similar 1.5 mm diameter titanium-6-4 alloy screw manufactured to retain bone implants. Results showed that carbon-fiber-reinforced composite stimulated osseointegration inside the tibia bone marrow measured as percent bone area (PBA to a great extent when compared to the titanium-6-4 alloy at statistically significant levels. PBA increased significantly with the carbon-fiber composite over the titanium-6-4 alloy for distances from the implant surfaces of 0.1 mm at 77.7% vs. 19.3% (p < 10−8 and 0.8 mm at 41.6% vs. 19.5% (p < 10−4, respectively. The review focuses on carbon fiber properties that increased PBA for enhanced implant osseointegration. Carbon fibers acting as polymer coated electrically conducting micro-biocircuits appear to provide a biocompatible semi-antioxidant property to remove damaging electron free radicals from the surrounding implant surface. Further, carbon fibers by removing excess electrons produced from the cellular mitochondrial electron transport chain during periods of hypoxia perhaps stimulate bone cell recruitment by free-radical chemotactic influences. In addition, well-studied bioorganic cell actin carbon fiber growth would appear to interface in close contact with the carbon-fiber-reinforced composite implant. Resulting subsequent actin carbon fiber/implant carbon fiber contacts then could help in discharging the electron biological overloads through electrochemical gradients to lower negative charges and lower concentration.

Carbon footprint of electronic devices

Science.gov (United States)

Sloma, Marcin

2013-07-01

Paper assesses the greenhouse gas emissions related to the electronic sectors including information and communication technology and media sectors. While media often presents the carbon emission problem of other industries like petroleum industry, the airlines and automobile sectors, plastics and steel manufacturers, the electronics industry must include the increasing carbon footprints caused from their applications like media and entertainment, computers and cooling devices, complex telecommunications networks, cloud computing and powerful mobile phones. In that sense greenhouse gas emission of electronics should be studied in a life cycle perspective, including regular operational electricity use. Paper presents which product groups or processes are major contributors in emission. From available data and extrapolation of existing information we know that the information and communication technology sector produced 1.3% and media sector 1.7% of global gas emissions within production cycle, using the data from 2007.In the same time global electricity use of that sectors was 3.9% and 3.2% respectively. The results indicate that for both sectors operation leads to more gas emissions than manufacture, although impacts from the manufacture is significant, especially in the supply chain. Media electronics led to more emissions than PCs (manufacture and operation). Examining the role of electronics in climate change, including disposal of its waste, will enable the industry to take internal actions, leading to lowering the impact on the climate change within the sector itself.

Stimulated Raman scattering and hot-electron production

International Nuclear Information System (INIS)

Drake, R.P.; Turner, R.E.; Lasinski, B.F.; Estabrook, K.G.; Campbell, E.M.; Wang, C.L.; Phillion, D.W.; Williams, E.A.; Kruer, W.L.

1985-01-01

High-intensity laser light can excite parametric instabilities that scatter or absorb it. One instability that can arise when laser light penetrates a plasma is sub-quarter-critical stimulated Raman (SQSR) scattering. It occurs below the quarter-critical density of the incident light and involves the decay of the incident light wave into a scattered light wave and electron plasma wave. The scattered-light wavelength ranges from 1 to 2 times that of the incident light, depending on the plasma density and temperature. This article reports studies of SQSR scattering and hot-electron production in plasmas produced by irradiating thick gold targets with up to 4 kJ of 0.53-μm light in 1-ns (FWHM) pulses. These studies have important implications for laser fusion. Hot electrons attributed to the SQSR instability can increase the difficulty of achieving high-gain implosions by penetrating and preheating the fusion fuel

Electronics with carbon nanotubes

International Nuclear Information System (INIS)

Avouris, P.

2007-01-01

From mobile phones and laptops to Xboxes and iPods, it is difficult to think of any aspect of modern life that has not been touched by developments in electronics, computing and communications over the last few decades. Many of these technological advances have arisen from our ability to create ever smaller electronic devices, in particular silicon-based field effect transistors (FETs), which has led to denser, faster and less power-hungry circuits. The problem is that this device miniaturization, or 'scaling', cannot continue forever. Fundamental scientific and technological limitations exist that will make it impossible to build better performing silicon devices below a certain size. This potential show-stopper has inspired a worldwide effort to develop alternative device technologies based on 1D materials or those that exploit the spin, as well as the charge, of electrons. One promising and, in principle, simpler approach is to maintain the operating concept of today's silicon-based FETs but to replace a key component of the device - the semiconducting silicon channel - with 1D nanostructures that have much more versatile electrical-transport properties. Among the different 1D materials that have been developed, those with the most desirable properties are 'single-walled' carbon nanotubes, which were first created in 1993 by Sumio Ijima at the NEC Fundamental Research Laboratory in Tsukuba, Japan, and by Donald Bethune of IBM's Almaden Research Center in California. These materials are hollow tubes made from rolled up sheets of carbon just one atom thick, otherwise known as graphene. In the March issue of Physics World, Phaedon Avouris discusses some of the many properties and applications of carbon nanotubes, which he describes as an 'engineer's dream' because of their exceptionally high strength and heat conduction. (U.K.)

The use of stimulated electron emission (SEE) in homeland security applications

Science.gov (United States)

Ing, H.; Andrews, H. R.; Facina, M.; Lee, W. T.; Niu, H. W.

2012-06-01

Certain insulating solids can store a fraction of the absorbed energy when irradiated by ionizing radiation. The stored energy can be released subsequently by heating or optical stimulation. As a result, light may be emitted through Thermoluminescence (TL) or Optically-Stimulated Luminescence (OSL) and electrons may be emitted through Thermally-Stimulated Electron Emission (TSEE) or Optically-Stimulated Electron Emission (OSEE). TL and OSL are widely used in current radiation dosimetry systems. However, despite considerable research effort during the early 1970s, SEE was not commonly adopted for dosimetry applications. One of the main reasons is that SEE is a surface phenomenon, while luminescence is a bulk phenomenon, making SEE more susceptible to humidity, absorption of gases, minor physical defects and handling, both before and after irradiation. Nevertheless, it has been recognized that SEE may be useful for homeland security applications in nuclear forensics, where dose accuracy is not the primary performance metric. In this research, we are investigating the use of SEE for nuclear forensic applications. Many common materials, both natural and man-made, exhibit the phenomenon, providing an opportunity to use the environment itself as an in-situ radiation detector. We have designed and constructed a unique prototype reader for conducting SEE measurements. We have demonstrated that the SEE measurements from a variety of materials are quantitatively reproducible and correlated to radiation exposure. Due to the broad applicability of SEE, significant additional studies are warranted to optimize this novel technique for nuclear forensic and other applications.

Study on regeneration of activated carbon by means of electron radiation

International Nuclear Information System (INIS)

Zhu Guanghua; Arai, H.; Hosono, M.

1991-01-01

The results of regeneration of activated carbon adsorbing sodium lauryl sulfate (SLS) by 2 MeV electron radiation, and the dependence of the regeneration rate of activated carbon on the electron current intensity, the temperature of sample and the atmosphere were reported. It is shown that regeneration of activated carbon by electron radiation is full of promise

Visible Light Neural Stimulation on graphitic-Carbon Nitride/Graphene Photocatalytic Fibers

DEFF Research Database (Denmark)

Zhang, Zhongyang; Xu, Ruodan; Wang, Zegao

2017-01-01

conversion, was for the first time investigated. Specifically, g-C3N4 was combined with graphene oxide (GO) in a 3D manner on the surfaces of electrospun polycaprolactone/gelatin (PG) fibers and functioned as a biocompatible interface for visible-light stimulating neuronal differentiation. The enhanced......Light stimulation allows remote and spatiotemporally accurate operation that has been applied as effective, non-invasive means of therapeutic interventions. Here, visible light neural stimulation of graphitic carbon nitride (g-C3N4), an emerging photocatalyst with visible-light optoelectronic...... was confirmed by the Lactate Dehydrogenase (LDH) assay, live dead staining and colorimetric cell viability assay CCK-8. Under a bidaily, monochromatic light stimulation at a wavelength of 450 nm at 10mW/cm2, a 18.5-fold increase of neurite outgrowth of PC12 was found on g-C3N4 coated fibers; while AA reduced GO...

Electronic structure of incident carbon ions on a graphite surface

International Nuclear Information System (INIS)

Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

1997-01-01

The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

Promoting direct interspecies electron transfer with activated carbon

DEFF Research Database (Denmark)

Liu, Fanghua; Rotaru, Amelia-Elena; Shrestha, Pravin M.

2012-01-01

Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC’s stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation...

Electron energy deposition in a multilayered carbon--uranium--carbon configuration and in semi-infinite uranium

International Nuclear Information System (INIS)

Lockwood, G.J.; Miller, G.H.; Halbleib, J.A. Sr.

1977-10-01

Absolute measurements of electron energy deposition profiles are reported here for electrons incident on the multilayer configuration of carbon-uranium-carbon. These measurements were for normally incident source electrons at an energy of 1.0 MeV. To complement these measurements, electron energy deposition profiles were also obtained for electrons incident on semi-infinite uranium as a function of energy and angle of incidence. The results are compared with the predictions of a coupled electron/photon Monte Carlo transport model. In general, the agreement between theory and experiment is good. This work was in support of the Reactor Safety Research Equation-of-State Program

Fullerenes, carbon nanotubes, and graphene for molecular electronics.

Science.gov (United States)

Pinzón, Julio R; Villalta-Cerdas, Adrián; Echegoyen, Luis

2012-01-01

With the constant growing complexity of electronic devices, the top-down approach used with silicon based technology is facing both technological and physical challenges. Carbon based nanomaterials are good candidates to be used in the construction of electronic circuitry using a bottom-up approach, because they have semiconductor properties and dimensions within the required physical limit to establish electrical connections. The unique electronic properties of fullerenes for example, have allowed the construction of molecular rectifiers and transistors that can operate with more than two logical states. Carbon nanotubes have shown their potential to be used in the construction of molecular wires and FET transistors that can operate in the THz frequency range. On the other hand, graphene is not only the most promising material for replacing ITO in the construction of transparent electrodes but it has also shown quantum Hall effect and conductance properties that depend on the edges or chemical doping. The purpose of this review is to present recent developments on the utilization carbon nanomaterials in molecular electronics.

A monoenergetic electron source generated by nuclear stimulated desorption

International Nuclear Information System (INIS)

Kelson, I.; Levy, Y.; Nir, D.; Haustein, P.E.

1994-01-01

A series of measurements of nuclear stimulated desorption was performed for 103 Ru, using thin ruthenium films irradiated by thermal neutrons. The magnitude, time dependence and electric charge state of the outgoing 103m Rh flux was investigated. The utilization of monoenergetic electrons accompanying the 103 Rh decay for thin film thickness measurement is considered. (Author)

Carbon Nanotube Based Molecular Electronics

Science.gov (United States)

Srivastava, Deepak; Saini, Subhash; Menon, Madhu

1998-01-01

Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

Dissolved organic carbon leaching from plastics stimulates microbial activity in the ocean

NARCIS (Netherlands)

Romera-Castillo, C.; Pinto, M.; Langer, T.M.; Alvarez-Salgado, X.A.; Herndl, G.

2018-01-01

Approximately 5.25 trillion plastic pieces are floating at the sea surface. The impact of plastic pollution on the lowest trophic levels of the food web, however, remains unknown. Here we show that plastics release dissolved organic carbon (DOC) into the ambient seawater stimulating the activity of

Modelling of electronic and vibrational properties of carbon nanostructures

Science.gov (United States)

Margine, Elena Roxana

The main goals of this dissertation work are the analysis and prediction of the properties of nanoscale carbon materials which hold great potential for nanotechnological applications such as strong conductive composites, field-effect transistors, diodes, rechargeable batteries, etc. Some of these exciting applications are already being actively developed, however their design via trial-and-error experimentation is often difficult and expensive. State-of-the-art simulation methods can be used as a powerful tool to streamline the path to practical implementations. In this thesis I use ab initio quantum-mechanical calculations to explore the response of nanoscale carbon materials to doping. A brief overview of the theoretical methods and of some basic concepts on carbon nanotubes are given in the first two chapters. In Chapter 3 we study the effect of doping in double-walled carbon nanotubes. These systems can be considered as nanoscale capacitors since they have two conducting (or semi-conducting) shells. The experimental work of our collaborators demonstrated for the first time that such a capacitor can be realized by the adsorption of bromine anions at the surface of the outer tube. Our theoretical analysis of the experimental results revealed that this quantum system, surprisingly, behaves exactly as the classical Faraday cage: the electric charge always resides on the outside surface of the conductor, even when the pristine tubes are not metallic. In Chapter 4 I present our findings on the phonon frequencies' response to electron doping in single-walled carbon nanotubes. It is well established that when graphite is doped with electrons, carbon-carbon bonds lengthen and all vibrational frequencies soften. However, in semiconducting carbon nanotubes, the frequency of one mode increases at low levels of alkali doping. Having carefully modelled the process with ab initio methods we conclude that the unusual behavior of the vibrational mode depends on which electronic

Monte Carlo simulation of positron induced secondary electrons in thin carbon foils

International Nuclear Information System (INIS)

Cai, L H; Yang, B; Ling, C C; Beling, C D; Fung, S

2011-01-01

Emission of secondary electrons induced by the passage of low energy positrons through thin carbon foils was studied by the Monte Carlo method. The positron and electron elastic cross sections were calculated by partial wave analysis. The inelastic positron-valence-electron was described by the energy loss function obtained from dielectric theory. The positron-core-electron interaction was modelled by the Gryzinski's excitation function. Positron transport inside the carbon foil was simulated in detail. Secondary electrons created by positrons and high energy secondary electrons through inelastic interactions were tracked through the foil. The positron transmission coefficient and secondary electron yielded in forward and backward geometry are calculated and dependences on positron energy and carbon foil thickness are discussed.

Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site

Science.gov (United States)

Buss, Joshua A.; Agapie, Theodor

2016-01-01

Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging. Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources. Electrocatalytic reduction of carbon monoxide on copper catalysts also uses a combination of electrons and protons, while the industrial Fischer-Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures. However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon-oxygen bonds and generate carbon-carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl-diphosphine ligand, that activates and cleaves the strong carbon-oxygen bond of carbon monoxide, enacts carbon-carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl-diphosphine ligand, which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for

Fabrication of carbon quantum dots with nano-defined position and pattern in one step via sugar-electron-beam writing.

Science.gov (United States)

Weng, Yuyan; Li, Zhiyun; Peng, Lun; Zhang, Weidong; Chen, Gaojian

2017-12-14

Quantum dots (QDs) are promising materials in nanophotonics, biological imaging, and even quantum computing. Precise positioning and patterning of QDs is a prerequisite for realizing their actual applications. Contrary to the traditional two discrete steps of fabricating and positioning QDs, herein, a novel sugar-electron-beam writing (SEW) method is reported for producing QDs via electron-beam lithography (EBL) that uses a carefully chosen synthetic resist, poly(2-(methacrylamido)glucopyranose) (PMAG). Carbon QDs (CQDs) could be fabricated in situ through electron beam exposure, and the nanoscale position and luminescence intensity of the produced CQDs could be precisely controlled without the assistance of any other fluorescent matter. We have demonstrated that upon combining an electron beam with a glycopolymer, in situ production of CQDs occurs at the electron beam spot center with nanoscale precision at any place and with any patterns, an advancement that we believe will stimulate innovations in future applications.

The use of angle resolved electron and photon stimulated desorption for the determination of molecular structure at surfaces

International Nuclear Information System (INIS)

Madey, T.E.; Stockbauer, R.

1983-01-01

A brief review of recent data related to the use of angle-resolved electron stimulated desorption and photon stimulated desorption in determining the structures of molecules at surfaces is made. Examples include a variety of structural assignments based on ESIAD (electron stimulated desorption ion angular distributions), the observation of short-range local ordering effects induced in adsorbed molecules by surface impurities, and the application of photon stimulated desorption to both ionic and covalent adsorbate systems. (Author) [pt

Acetaldehyde stimulation of net gluconeogenic carbon movement from applied malic acid in tomato fruit pericarp tissue

International Nuclear Information System (INIS)

Halinska, A.; Frenkel, C.

1991-01-01

Applied acetaldehyde is known to lead to sugar accumulation in fruit including tomatoes (Lycopersicon esculentum) presumably due to stimulation of gluconeogenesis. This conjecture was examined using tomato fruit pericarp discs as a test system and applied l-[U- 14 C]malic acid as the source for gluconeogenic carbon mobilization. Results indicate that malic and perhaps other organic acids are carbon sources for gluconeogenesis occurring normally in ripening tomatoes. The process is stimulated by acetaldehyde apparently by attenuating the fructose-2,6-biphosphate levels. The mode of the acetaldehyde regulation of fructose-2,6-biphosphate metabolism awaits clarification

Electronic resonances in broadband stimulated Raman spectroscopy

Science.gov (United States)

Batignani, G.; Pontecorvo, E.; Giovannetti, G.; Ferrante, C.; Fumero, G.; Scopigno, T.

2016-01-01

Spontaneous Raman spectroscopy is a formidable tool to probe molecular vibrations. Under electronic resonance conditions, the cross section can be selectively enhanced enabling structural sensitivity to specific chromophores and reaction centers. The addition of an ultrashort, broadband femtosecond pulse to the excitation field allows for coherent stimulation of diverse molecular vibrations. Within such a scheme, vibrational spectra are engraved onto a highly directional field, and can be heterodyne detected overwhelming fluorescence and other incoherent signals. At variance with spontaneous resonance Raman, however, interpreting the spectral information is not straightforward, due to the manifold of field interactions concurring to the third order nonlinear response. Taking as an example vibrational spectra of heme proteins excited in the Soret band, we introduce a general approach to extract the stimulated Raman excitation profiles from complex spectral lineshapes. Specifically, by a quantum treatment of the matter through density matrix description of the third order nonlinear polarization, we identify the contributions which generate the Raman bands, by taking into account for the cross section of each process.

Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

Science.gov (United States)

Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

2009-01-01

Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

Electronic Transport Parameter of Carbon Nanotube Metal-Semiconductor On-Tube Heterojunction

Directory of Open Access Journals (Sweden)

Sukirno

2009-03-01

Full Text Available Carbon Nanotubes research is one of the top five hot research topics in physics since 2006 because of its unique properties and functionalities, which leads to wide-range applications. One of the most interesting potential applications is in term of nanoelectronic device. It has been modeled carbon nanotubes heterojunction, which was built from two different carbon nanotubes, that one is metallic and the other one is semiconducting. There are two different carbon nanotubes metal-semiconductor heterojunction. The first one is built from CNT(10,10 as metallic carbon nanotube and CNT (17,0 as semiconductor carbon nanotube. The other one is built from CNT (5,5 as metallic carbon nanotube and CNT (8,0. All of the semiconducting carbon nanotubes are assumed to be a pyridine-like N-doped. Those two heterojunctions are different in term of their structural shape and diameter. It has been calculated their charge distribution and potential profile, which would be useful for the simulation of their electronic transport properties. The calculations are performed by using self-consistent method to solve Non-Homogeneous Poisson’s Equation with aid of Universal Density of States calculation method for Carbon Nanotubes. The calculations are done by varying the doping fraction of the semiconductor carbon nanotubes The electron tunneling transmission coefficient, for low energy region, also has been calculated by using Wentzel-Kramer-Brillouin (WKB approximation. From the calculation results, it is obtained that the charge distribution as well as the potential profile of this device is doping fraction dependent. It is also inferred that the WKB method is fail to be used to calculate whole of the electron tunneling coefficient in this system. It is expected that further calculation for electron tunneling coefficient in higher energy region as well as current-voltage characteristic of this system will become an interesting issue for this carbon nanotube based

Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

Science.gov (United States)

Chen, Cheng; Fan, Xue; Diao, Dongfeng

2016-10-01

We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp2 nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp2 nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp2 nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

Bending of metal-filled carbon nanotube under electron beam irradiation

Directory of Open Access Journals (Sweden)

Abha Misra

2012-03-01

Full Text Available Electron beam irradiation induced, bending of Iron filled, multiwalled carbon nanotubes is reported. Bending of both the carbon nanotube and the Iron contained within the core was achieved using two approaches with the aid of a high resolution electron microscope (HRTEM. In the first approach, bending of the nanotube structure results in response to the irradiation of a pristine kink defect site, while in the second approach, disordered sites induce bending by focusing the electron beam on the graphite walls. The HRTEM based in situ observations demonstrate the potential for using electron beam irradiation to investigate and manipulate the physical properties of confined nanoscale structures.

Electron source with a carbon-fibrous cathode for radiation-technology accelerator

International Nuclear Information System (INIS)

Korenev, S.A.

1994-01-01

The paper analyses the circuit of a full operating voltage electron source which is a direct-action electron accelerator. The electron source consists of a power supply, high-voltage multiplier-rectifier, vacuum planar diode, vacuum system and control system. The vacuum electron diode contains an autoemission carbon-fibrous cathode and beryllium foil strip anode. The results of measurements of emission characteristics of alumosilicate and carbon-fibrous cathodes are presented. The investigations into test electron source show that it can be used as a basis for creating an electron accelerator which will be capable of generating 1 MW electron beams of 1-2 MeV energy and 1 A current. 3 refs., 1 fig., 1 tab

Carbon buildup monitoring using RBS: Correlation with secondary electrons

International Nuclear Information System (INIS)

Aguilera, E.F.; Rosales, P.; Martinez-Quiroz, E.; Murillo, G.; Fernandez, M.C.

2006-01-01

The RBS technique is applied to solve the problem of on-line monitoring of the carbon deposited on a thin backed foil under ion bombardment. An iterative method is used to reliably extract quantities such as number of projectiles and target thickness in spite of beam energy changes and detector unstabilities. Experimental values for secondary electron yields are also deduced. Results are reported for the thickness variation of thin carbon foils bombarded with carbon ions of energies between 8.95 and 13 MeV. A linear correlation of this variation is found with both, the ion fluence at target and the number of secondary electrons emitted. The correlation exists even though a wide range of beam currents, beam energies and bombarding times was used during the experiment. The measured electron yields show evidence for a change in the emission process between the original foils and the deposited layer, possibly due to a texture change

Electronic properties of prismatic modifications of single-wall carbon nanotubes

Science.gov (United States)

Tomilin, O. B.; Muryumin, E. E.; Rodionova, E. V.; Ryskina, N. P.

2018-01-01

The article shows the possibility of target modifying the prismatic single-walled carbon nanotubes (SWCNTs) by regular chemisorption of fluorine atoms in the graphene surface. It is shown that the electronic properties of prismatic SWCNT modifications are determined by the interaction of π- and ρ(in-plane)-electron conjugation in the carbon-conjugated subsystems (tracks) formed in the faces. The contributions of π- and ρ(in-plane)-electron conjugation depend on the structural characteristics of the tracks. It was found that the minimum of degree deviation of the track from the plane of the prism face and the maximum of the track width ensure the maximum contribution of the π-electron conjugation, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the hydrocarbon analog of the carbon track. It is established that the maximum of degree deviation of the track from the plane of the prism face and the maximum of track width ensure the maximum contribution of the ρ(in-plane) electron interface, and the band gap of the prismatic modifications of the SWCNT tends to the band gap of the unmodified carbon nanotube. The calculation of the model systems has been carried out using an ab initio Hartree-Fock method in the 3-21G basis.

Temperature dependences in electron-stimulated desorption of neutral europium

CERN Document Server

Ageev, V N; Madey, T E

2003-01-01

The electron-stimulated desorption (ESD) yield for neutral europium (Eu) atoms from Eu layers adsorbed on oxygen-covered tungsten surfaces has been measured as a function of electron energy, europium coverage and degree of oxidation of tungsten, with an emphasis on effects of substrate temperature. The measurements have been carried out using a time-of-flight method and surface ionization detector. We expand on an earlier report, and compare ESD of multivalent Eu with ESD of monovalent alkali atoms, studied previously. The Eu atom ESD is a complicated function of Eu coverage, electron energy and substrate temperature. In the coverage range 0.05-0.35 monolayer (ML), overlapping resonant-like Eu atom yield peaks are observed at electron energies E sub e of 36 and 41 eV that might be associated with Eu or W shallow core level excitations. Additional resonant-like peaks are seen at E sub e of 54 and 84 eV that are associated with W 5p and 5s level excitations. The Eu atom yield peaks at 36 and 41 eV are seen only...

Determination of low-energy ion-induced electron yields from thin carbon foils

International Nuclear Information System (INIS)

Allegrini, Frederic; Wimmer-Schweingruber, Robert F.; Wurz, Peter; Bochsler, Peter

2003-01-01

Ion beams crossing thin carbon foils can cause electron emission from the entrance and exit surface. Thin carbon foils are used in various types of time-of-flight (TOF) mass spectrometers to produce start pulses for TOF measurements. The yield of emitted electrons depends, among other parameters, on the energy of the incoming ion and its mass, and it has been experimentally determined for a few projectile elements. The electron emission yield is of great importance for deriving abundance ratios of elements and isotopes in space plasmas using TOF mass spectrometers. We have developed a detector for measuring ion-induced electron yields, and we have extended the electron yield measurements for oxygen to energies relevant for solar wind research. We also present first measurements of the carbon foil electron emission yield for argon and iron in the solar wind energy range

Using optically stimulated electrons from quartz for the estimation of natural doses

DEFF Research Database (Denmark)

Ankjærgaard, Christina; Murray, A.S.; Denby, Phil M.

2009-01-01

A flow-through Geiger-Müller pancake electron detector attachment has been fitted to a standard Risø TL/OSL reader enabling optically stimulated electrons (OSE) to be measured simultaneously with optically stimulated luminescence (OSL). Using this detector, OSE and OSL measurements from natural......, a dose recovery test shows that OSE can successfully recover a laboratory dose of 300 Gy given before any laboratory thermal treatment, for preheating temperatures between 160 and 260 °C. Furthermore, for the first time natural OSE decay curves are detected and these signals are used to estimate a burial...... dose using the single-aliquot regenerative-dose (SAR) procedure. Finally, a comparative study of the equivalent doses estimated using both OSE and OSL from 10 quartz samples are presented, and it is shown that OSE has a significant potential in retrospective dosimetry....

Bottom-up, Robust Graphene Ribbon Electronics in All-Carbon Molecular Junctions.

Science.gov (United States)

Supur, Mustafa; Van Dyck, Colin; Bergren, Adam J; McCreery, Richard L

2018-02-21

Large-area molecular electronic junctions consisting of 5-carbon wide graphene ribbons (GR) with lengths of 2-12 nm between carbon electrodes were fabricated by electrochemical reduction of diazotized 1,8-diaminonaphthalene. Their conductance greatly exceeds that observed for other molecular junctions of similar thicknesses, by a factor of >1 × 10 4 compared to polyphenylenes and >1 × 10 7 compared to alkane chains. The remarkable increase of conductance of the GR nanolayer results from (i) uninterrupted planarity of fused-arene structure affording extensive π-electron delocalization and (ii) enhanced electronic coupling of molecular layer with the carbon bottom contact by two-point covalent bonding, in agreement with DFT-based simulations.

Dimension-dependent stimulated radiative interaction of a single electron quantum wavepacket

Science.gov (United States)

Gover, Avraham; Pan, Yiming

2018-06-01

In the foundation of quantum mechanics, the spatial dimensions of electron wavepacket are understood only in terms of an expectation value - the probability distribution of the particle location. One can still inquire how the quantum electron wavepacket size affects a physical process. Here we address the fundamental physics problem of particle-wave duality and the measurability of a free electron quantum wavepacket. Our analysis of stimulated radiative interaction of an electron wavepacket, accompanied by numerical computations, reveals two limits. In the quantum regime of long wavepacket size relative to radiation wavelength, one obtains only quantum-recoil multiphoton sidebands in the electron energy spectrum. In the opposite regime, the wavepacket interaction approaches the limit of classical point-particle acceleration. The wavepacket features can be revealed in experiments carried out in the intermediate regime of wavepacket size commensurate with the radiation wavelength.

Vertically aligned multiwalled carbon nanotubes as electronic interconnects

Science.gov (United States)

Gopee, Vimal Chandra

The drive for miniaturisation of electronic circuits provides new materials challenges for the electronics industry. Indeed, the continued downscaling of transistor dimensions, described by Moore’s Law, has led to a race to find suitable replacements for current interconnect materials to replace copper. Carbon nanotubes have been studied as a suitable replacement for copper due to its superior electrical, thermal and mechanical properties. One of the advantages of using carbon nanotubes is their high current carrying capacity which has been demonstrated to be three orders of magnitude greater than that of copper. Most approaches in the implementation of carbon nanotubes have so far focused on the growth in vias which limits their application. In this work, a process is described for the transfer of carbon nanotubes to substrates allowing their use for more varied applications. Arrays of vertically aligned multiwalled carbon nanotubes were synthesised by photo-thermal chemical vapour deposition with high growth rates. Raman spectroscopy was used to show that the synthesised carbon nanotubes were of high quality. The carbon nanotubes were exposed to an oxygen plasma and the nature of the functional groups present was determined using X-ray photoelectron spectroscopy. Functional groups, such as carboxyl, carbonyl and hydroxyl groups, were found to be present on the surface of the multiwalled carbon nanotubes after the functionalisation process. The multiwalled carbon nanotubes were metallised after the functionalisation process using magnetron sputtering. Two materials, solder and sintered silver, were chosen to bind carbon nanotubes to substrates so as to enable their transfer and also to make electrical contact. The wettability of solder to carbon nanotubes was investigated and it was demonstrated that both functionalisation and metallisation were required in order for solder to bond with the carbon nanotubes. Similarly, functionalisation followed by metallisation

Self-grafting carbon nanotubes on polymers for stretchable electronics

Science.gov (United States)

Morales, Piero; Moyanova, Slavianka; Pavone, Luigi; Fazi, Laura; Mirabile Gattia, Daniele; Rapone, Bruno; Gaglione, Anderson; Senesi, Roberto

2018-06-01

Elementary bidimensional circuitry made of single-wall carbon-nanotube-based conductors, self-grafted on different polymer films, is accomplished in an attempt to develop a simple technology for flexible and stretchable electronic devices. Unlike in other studies of polymer-carbon nanotube composites, no chemical functionalization of single-wall carbon nanotubes is necessary for stable grafting onto several polymeric surfaces, suggesting viable and cheap fabrication technologies for stretchable microdevices. Electrical characterization of both unstretched and strongly stretched conductors is provided, while an insight on the mechanisms of strong adhesion to the polymer is obtained by scanning electron microscopy of the surface composite. As a first example of technological application, the electrical functionality of a carbon-nanotube-based 6-sensor (electrode) grid was demonstrated by recording of subdural electrocorticograms in freely moving rats over approximately three months. The results are very promising and may serve as a basis for future work targeting clinical applications.

Revealing the 1 nm/s Extensibility of Nanoscale Amorphous Carbon in a Scanning Electron Microscope

DEFF Research Database (Denmark)

Zhang, Wei

2013-01-01

In an ultra-high vacuum scanning electron microscope, the edged branches of amorphous carbon film (∼10 nm thickness) can be continuously extended with an eye-identifying speed (on the order of ∼1 nm/s) under electron beam. Such unusual mobility of amorphous carbon may be associated with deformation...... promoted by the electric field, which resulted from an inner secondary electron potential difference from the main trunk of carbon film to the tip end of branches under electron beam. This result demonstrates importance of applying electrical effects to modify properties of carbon materials. It may have...... positive implications to explore some amorphous carbon as electron field emission device. SCANNING 35: 261-264, 2013. © 2012 Wiley Periodicals, Inc....

Stimulation of plasma waves by electron guns on the ISEE-1 satellite

Science.gov (United States)

Lebreton, J.-P.; Torbert, R.; Anderson, R.; Harvey, C.

1982-01-01

The results of the ISEE-1 satellite experiment relating to observations of the waves stimulated during electron injections, when the spacecraft is passing through the magnetosphere, the magnetosheath, and the solar wind, are discussed. It is shown that the injection of an electron beam current of the order of 10 to 60 microamperes with energies ranging from 0 to 40 eV produces enhancements in the electric wave spectrum. An attempt has been made to identify the low-frequency electrostatic wave observed below the ion plasma frequency as an ion acoustic mode, although the excitation mechanism is not clear. A coupling mechanism between the electron plasma mode and streaming electrons with energies higher than the thermal speed of the cold electron population has been proposed to explain the observations above the electron plasma frequency.

Stimulation of plasma waves by electron guns on the ISEE-1 satellite

International Nuclear Information System (INIS)

Lebreton, J.P.; Anderson, R.; Harvey, C.; Torbert, R.

1982-01-01

This chapter describes typical observations of the waves stimulated during the electron injections, when the spacecraft is passing through the magnetosphere, the magnetosheath and the solar wind. Topics considered include orbits of gun electrons, an electric field antenna, gun operation in the magnetosphere, natural waves in the magnetosheath and the solar wind, gun operation magnetosheath, and gun operation in the solar wind. A coupling mechanism between the electron plasma mode and streaming electrons with energies higher than the thermal speed of the cold electron population is proposed to explain the observations above the electron plasma frequency. It is demonstrated that on board the ISEE-1 satellite, the injection of an electron beam current of the order of 10 to 60 251A with energies ranging from 0 to 40 eV produced enhancements in the electric wave spectrum

Hot electron-induced electrochemiluminescence at polyetherimide-carbon black-based electrodes

International Nuclear Information System (INIS)

Salminen, Kalle; Grönroos, Päivi; Johansson, Leena-Sisko; Campbell, Joseph; Kulmala, Sakari

2017-01-01

Highlights: • Generation of hydrated electrons at carbon paste electrodes. • Hydrated electrons are able to produce intense chemiluminescence. • Relationship between carbon black content in electrode and HECL studied. • Performance of composite electrodes is similar to aluminum electrodes. • The present electrodes are good alternative for disposable assay cartridges. - Abstract: Various luminophores produce strong electrogenerated chemiluminescence during cathodic pulse polarization of the present insulating film-covered carbon paste electrodes in fully aqueous solutions. First electrodes made of a commercial conductive carbon paste were successfully utilized as working electrodes and their surface was characterized by ESCA. Then custom in-laboratory made improved composite electrodes were manufactured from the same insulating polymer and conducting carbon black particles. The relationship between the amount of carbon present on the composite electrode, in the bulk and on the surface, and the intensity of electrogenerated chemiluminescence was studied further. The overall performance of these composite electrodes makes them viable low-cost replacements for metal/insulator type electrodes such as oxide-coated silicon electrodes.

Enhanced electromagnetic properties of nickel nanoparticiles dispersed carbon fiber via electron beam irradiation

International Nuclear Information System (INIS)

Lee, Yeong Ju; Kim, Hyun Bin; Lee, Seung Jun; Kang, Phil Hyun

2015-01-01

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications

Enhanced electromagnetic properties of nickel nanoparticiles dispersed carbon fiber via electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Lee, Yeong Ju; Kim, Hyun Bin; Lee, Seung Jun; Kang, Phil Hyun [Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

2015-02-15

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.

Simulation and Optimization of a Carbon Nanotube Electron Source

Czech Academy of Sciences Publication Activity Database

Knápek, Alexandr; Radlička, Tomáš; Krátký, Stanislav

2015-01-01

Roč. 21, S4 (2015), s. 60-65 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : carbon nanotube * electron beam lithography Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

Electron momentum spectroscopy of the core state of solid carbon

International Nuclear Information System (INIS)

Caprari, R.S.; Clark, S.A.C.; McCarthy, I.E.; Storer, P.J.; Vos, M.; Weigold, E.

1994-08-01

Electron momentum spectroscopy (binary encounter (e,2e)) experimental results are presented for the core state of an amorphous carbon allotrope. The (e,2e) cross section has two identifiable regions. One is a narrow energy width 'core band peak' that does not disperse with momentum. At higher binding energies there is an energy diffuse 'multiple scattering continuum', which is a consequence of (e,2e) collisions with core electrons that are accompanied by inelastic scattering of one or more of the incoming or outgoing electrons. Comparisons of experimental momentum distributions with the Hartree-Fock atomic carbon ls orbital are presented for both regions. 16 refs., 4 figs

Carbonate counter pump stimulated by natural iron fertilization in the Polar Frontal Zone

Science.gov (United States)

Salter, Ian; Schiebel, Ralf; Ziveri, Patrizia; Movellan, Aurore; Lampitt, Richard; Wolff, George A.

2014-12-01

The production of organic carbon in the ocean's surface and its subsequent downward export transfers carbon dioxide to the deep ocean. This CO2 drawdown is countered by the biological precipitation of carbonate, followed by sinking of particulate inorganic carbon, which is a source of carbon dioxide to the surface ocean, and hence the atmosphere over 100-1,000 year timescales. The net transfer of CO2 to the deep ocean is therefore dependent on the relative amount of organic and inorganic carbon in sinking particles. In the Southern Ocean, iron fertilization has been shown to increase the export of organic carbon, but it is unclear to what degree this effect is compensated by the export of inorganic carbon. Here we assess the composition of sinking particles collected from sediment traps located in the Polar Frontal Zone of the Southern Ocean. We find that in high-nutrient, low-chlorophyll regions that are characterized by naturally high iron concentrations, fluxes of both organic and inorganic carbon are higher than in regions with no iron fertilization. However, the excess flux of inorganic carbon is greater than that of organic carbon. We estimate that the production and flux of carbonate in naturally iron-fertilized waters reduces the overall amount of CO2 transferred to the deep ocean by 6-32%, compared to 1-4% at the non-fertilized site. We suggest that an increased export of organic carbon, stimulated by iron availability in the glacial sub-Antarctic oceans, may have been accompanied by a strengthened carbonate counter pump.

An AES Study of the Room Temperature Surface Conditioning of Technological Metal Surfaces by Electron Irradiation

CERN Document Server

Scheuerlein, C; Taborelli, M; Brown, A; Baker, M A

2002-01-01

The modifications to technological copper and niobium surfaces induced by 2.5 keV electron irradiation have been investigated in the context of the conditioning process occurring in particle accelerator ultra high vacuum systems. Changes in the elemental surface composition have been found using Scanning Auger Microscopy (SAM) by monitoring the carbon, oxygen and metal Auger peak intensities as a function of electron irradiation in the dose range 10-6 to 10-2 C mm-2. The surface analysis results are compared with electron dose dependent secondary electron and electron stimulated desorption yield measurements. Initially the electron irradiation causes a surface cleaning through electron stimulated desorption, in particular of hydrogen. During this period both the electron stimulated desorption and secondary electron yield decrease as a function of electron dose. When the electron dose exceeds 10-4 C mm-2 electron stimulated desorption yields are reduced by several orders of magnitude and the electron beam indu...

Fabrication of carbon layer coated FE-nanoparticles using an electron beam irradiation

Science.gov (United States)

Kim, Hyun Bin; Jeun, Joon Pyo; Kang, Phil Hyun; Oh, Seung-Hwan

2016-01-01

A novel synthesis of carbon encapsulated Fe nanoparticles was developed in this study. Fe chloride (III) and polyacrylonitrile (PAN) were used as precursors. The crosslinking of PAN molecules and the nucleation of Fe nanoparticles were controlled by the electron beam irradiation dose. Stabilization and carbonization processes were carried out using a vacuum furnace at 275 °C and 1000 °C, respectively. Micro structures were evaluated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fe nanoparticles were formed with diameters of 100 nm, and the Fe nanoparticles were encapsulated by carbon layers. As the electron beam irradiation dose increased, it was observed that the particle sizes decreased.

Stimulation of plasma waves by electron guns on the ISEE-1 satellite

International Nuclear Information System (INIS)

Lebreton, J.P.; Torbert, R.; Anderson, R.; Harvey, C.

1982-01-01

The results of the ISEE-1 satellite experiment relating to observations of the waves stimulated during electron injections, when the spacecraft is passing through the magnetosphere, the magnetosheath, and the solar wind, are discussed. It is shown that the injection of an electron beam current of the order of 10 to 60 microamperes with energies ranging from 0 to 40 eV produces enhancements in the electric wave spectrum. An attempt has been made to identify the low-frequency electrostatic wave observed below the ion plasma frequency as an ion acoustic mode, although the excitation mechanism is not clear. A coupling mechanism between the electron plasma mode and streaming electrons with energies higher than the thermal speed of the cold electron population has been proposed to explain the observations above the electron plasma frequency. 9 references

Electron uptake by iron-oxidizing phototrophic bacteria

Energy Technology Data Exchange (ETDEWEB)

Bose, A; Gardel, EJ; Vidoudez, C; Parra, EA; Girguis, PR

2014-02-26

Oxidation-reduction reactions underlie energy generation in nearly all life forms. Although most organisms use soluble oxidants and reductants, some microbes can access solid-phase materials as electron-acceptors or -donors via extracellular electron transfer. Many studies have focused on the reduction of solid-phase oxidants. Far less is known about electron uptake via microbial extracellular electron transfer, and almost nothing is known about the associated mechanisms. Here we show that the iron-oxidizing photoautotroph Rhodopseudomonas palustris TIE-1 accepts electrons from a poised electrode, with carbon dioxide as the sole carbon source/electron acceptor. Both electron uptake and ruBisCo form I expression are stimulated by light. Electron uptake also occurs in the dark, uncoupled from photosynthesis. Notably, the pioABC operon, which encodes a protein system essential for photoautotrophic growth by ferrous iron oxidation, influences electron uptake. These data reveal a previously unknown metabolic versatility of photoferrotrophs to use extracellular electron transfer for electron uptake.

Optical Performance of Carbon-Nanotube Electron Sources

International Nuclear Information System (INIS)

Jonge, Niels de; Allioux, Myriam; Oostveen, Jim T.; Teo, Kenneth B. K.; Milne, William I.

2005-01-01

The figure of merit for the electron optical performance of carbon-nanotube (CNT) electron sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art electron point sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter

Electron beam interactions with CO on W[100] studied by Auger electron spectroscopy

International Nuclear Information System (INIS)

Housley, M.; King, D.A.

1977-01-01

The interaction of 2500 eV electrons with carbon monoxide chemisorbed on tungsten [100] was investigated by rapid-scan Auger electron spectroscopy. When no α state was present the O and C signals from the β state of CO were invariant during electron bombardment, giving an upper limit estimate for the electron stimulated desorption cross section, Qsub(β), of 2 x 10 -21 cm 2 . With the crystal at room temperature and saturated with CO, however, electron-beam induced accumulation of carbon was observed and characterised, the rate of the process being independent of CO pressure at pressures above 2 x 10 -8 Torr. At 450 K the rate was found to be pressure dependent up to at least 6 x 10 -7 Torr. A model is proposed for the accumulation process, which is based on electron beam dissociation of α 2 -CO to form adsorbed carbon and gaseous O and the creation of new sites for further α 2 -CO adsorption; it is in quantitative agreement with the results and yields a cross section for ESD of α 2 -CO (Qsub(α 2 )=1.55 X 10 -18 cm 2 ) in clo 2 e agreement with direct measurements. (Auth.)

Humidity effects on the electronic transport properties in carbon based nanoscale device

International Nuclear Information System (INIS)

He, Jun; Chen, Ke-Qiu

2012-01-01

By applying nonequilibrium Green's functions in combination with the density functional theory, we investigate the effect of humidity on the electronic transport properties in carbon based nanoscale device. The results show that different humidity may form varied localized potential barrier, which is a very important factor to affect the stability of electronic transport in the nanoscale system. A mechanism for the humidity effect is suggested. -- Highlights: ► Electronic transport in carbon based nanoscale device. ► Humidity affects the stability of electronic transport. ► Different humidity may form varied localized potential barrier.

A biosensor for hydrogen peroxide detection based on electronic properties of carbon nanotubes

Science.gov (United States)

Majidi, Roya

2013-01-01

Density functional theory has been used to study the effect of hydrogen peroxide on the electronic properties of single walled carbon nanotubes. The metallic and semiconducting carbon nanotubes have been considered in the presence of different number of hydrogen peroxide. The results indicate that hydrogen peroxide has no significant effect on the metallic nanotube and these nanotubes remain to be metallic. In contrast, the electronic properties of the semiconducting nanotubes are so sensitive to hydrogen peroxide. The energy band gap of these nanotubes is decreased by increasing the number of hydrogen peroxide. The electronic sensivity of the carbon nanotubes to hydrogen peroxide opens new insights into developing biosensors based on the single walled carbon nanotubes.

Regeneration of used activated carbon by electron beam irradiation

International Nuclear Information System (INIS)

Arai, H.; Hosono, M.; Zhu, G.; Miyata, T.

1992-01-01

The adsorbing power of granular activated carbons which adsorbed sodium laurylsulfate were most effectively recovered by irradiation of high energy electron beams in nitrogen stream, and the carbon was hardly lost by irradiation. The regeneration was induced mainly by microscopic heating of adsorption sites. Regeneration was also confirmed by adsorption endotherms. Regeneration cost was tentatively evaluated. (author)

Multi-pulsed intense electron beam emission from velvet, carbon fibers, carbon nano-tubes and dispenser cathodes

International Nuclear Information System (INIS)

Xia Liansheng; Yang Anmin; Chen Yi; Zhang Huang; Liu Xingguang; Li Jin; Jiang Xiaoguo; Zhang Kaizhi; Shi Jinshui; Deng Jianjun; Zhang Linwen

2010-01-01

The experimental results of studies of four kinds of cathode emitting intense electron beams are demonstrated under multi-pulsed mode based on an experimental setup including two multi-pulse high voltage sources. The tested cathodes include velvet, carbon fibers, carbon nano-tubes (CNTs) and dispenser cathodes. The results indicate that all four are able to emit multi-pulsed beams. For velvet, carbon fiber and CNTs, the electron induced cathode plasma emission may be the main process and this means that there are differences in beam parameters from pulse to pulse. For dispenser cathodes tested in the experiment, although there is a little difference from pulse to pulse for some reason, thermal-electric field emission may be the main process. (authors)

Secondary electron yields of carbon-coated and polished stainless steel

International Nuclear Information System (INIS)

Ruzic, D.; Moore, R.; Manos, D.; Cohen, S.

1982-01-01

To increase the power throughput to a plasma of an existing lower hybrid waveguide, secondary electron production on the walls and subsequent electron multiplication must be reduced. Since carbon has a low secondary electron coefficient (delta), measurements were performed for several UHV compatible carbon coatings (Aquadag/sup X/, vacuum pyrolyzed Glyptal/sup X/, and lamp black deposited by electrophoresis) as a function of primary beam voltage (35 eV to 10 keV), surface roughness (60 through 600 grit mechanical polishing and electropolishing), coating thickness, and angle of incidence (theta). Also measured were uncoated stainless steel, Mo, Cu, Ti, TiC, and ATJ graphite. The yields were obtained by varying the sample bias and measuring the collected current while the samples were in the electron beam of a scanning Auger microprobe. This technique allows delta measurements of Auger characterized surfaces with < or =0.3 mm spatial resolution. Results show delta to have a typical energy dependence, with a peak occurring at 200 to 300 eV for normal incidence, and at higher energy for larger theta. In general, delta increases with theta more for smooth surfaces than for rough ones. Ninety percent of the secondary electrons have energies less than 25 eV. Some carbonized coating and surface treatment combinations give delta/sub max/ = 0.88 +- 0.01 for normal electron beam incidence: a reduction of almost 40% compared to untreated stainless steel

Conformational analysis and electronic structure of chiral carbon and carbon nitride nanotubes

Directory of Open Access Journals (Sweden)

Cristiano Geraldo de Faria

2011-12-01

Full Text Available Geometry and electronic structure of chiral carbon and carbon nitride (CNx nanotubes were investigated through quantum chemical methods. Finite nanotubes with diameters ranging from 5 to 10 Å and containing up to 500 atoms were considered. CNx structures were built through random substitution of carbon atoms by nitrogen. The molecules were fully optimized by semi-empirical quantum chemical method (PM3. Our results show that the energy associated with nitrogen incorporation depends strongly upon the tube helicity and diameter. The doping of nanotubes with nitrogen contributes to reduce the stress caused by the small diameter of the studied systems. Density of States (DOS results for pure carbon and CNx nanostructures, obtained through DFT and Hartree-Fock calculations, were analyzed. The introduction of nitrogen in the tube produce states in the gap region which characterizes the metallic behavior, as expected for these systems after N-doping.

Charging of carbon thin films in scanning and phase-plate transmission electron microscopy

DEFF Research Database (Denmark)

Hettler, Simon; Kano, Emi; Dries, Manuel

2018-01-01

A systematic study on charging of carbon thin films under intense electron-beam irradiation was performed in a transmission electron microscope to identify the underlying physics for the functionality of hole-free phase plates. Thin amorphous carbon films fabricated by different deposition techni...

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

International Nuclear Information System (INIS)

Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

2011-01-01

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

Energy Technology Data Exchange (ETDEWEB)

Hojati-Talemi, Pejman [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Mawson Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Gibson, Mark A. [Process Science and Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, Vic 3168 (Australia); East, Daniel; Simon, George P. [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

2011-11-07

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

Electronically stimulated deep-center reactions in electron-irradiated InP: Comparison between experiment and recombination-enhancement theories

International Nuclear Information System (INIS)

Sibille, A.

1987-01-01

We present a detailed study of the recombination enhancement of several defect reactions involving the main deep centers in low-temperature electron-irradiated InP. A fairly good agreement is obtained with the Weeks-Tully-Kimerling theory for the activation energies of the enhanced process. On the other hand, a thorough investigation of a thermally and electronically stimulated defect transformation shows evidence that one major approximation (local vibrational equilibrium) fails, and that the recently proposed [H. Sumi, Phys. Rev. B 29, 4616 (1984)] mechanism of coherent recombination on deep centers is responsible for altered reaction rates at high injection levels

Recent advances in carbon nanotube-based electronics

International Nuclear Information System (INIS)

Sharma, Prithu; Ahuja, Prerit

2008-01-01

CNT-electronics is a field involving synthesis of carbon nanotubes-based novel electronic circuits, comparable to the size of molecules, the practically fundamental size possible. It has brought a new paradigm in science as it has enabled scientists to increase the device integration density tremendously, hence achieving better efficiency and speed. Here we review the state-of-art current research on the applications of CNTs in electronics and present recent results outlining their potential along with illustrating some current concerns in the research field. Unconventional projects such as CNT-based biological sensors, transistors, field emitters, integrated circuits, etc. are taking CNT-based electronics to its extremes. The field holds a promise for mass production of high speed and efficient electronic devices. However, the chemical complexity, reproducibility and other factors make the field a challenging one, which need to be addressed before the field realizes its true potential

Electronic properties of single-walled chiral carbon nanotube

International Nuclear Information System (INIS)

Mensah, S.Y.; Allotey, F.K.A.; Mensah, N.G.; Nkrumah, G.

2001-09-01

The electronic properties of single-walled chiral carbon nanotube has been studied using the model based on infinitely long carbon atoms wrapped along a base helix of single-walled carbon nanotubes(SWNTs). The problem is solved semiclassically, and current density J, resistivity ρ, thermopower α z , and electrical power factor P calculated. It is noted that the current density j displays negative differential conductivity, whiles the resistivity ρ increases with increasing electrical field. ρ also slowly increases at low temperatures and then gradually increases with increasing temperature. The thermopower α z shows interesting behaviour. Very intriguing is the electrical power factor which shows relatively large values. (author)

Inorganic carbon addition stimulates snow algae primary productivity

Science.gov (United States)

Hamilton, T. L.; Havig, J. R.

2017-12-01

Earth has experienced glacial/interglacial oscillations throughout its history. Today over 15 million square kilometers (5.8 million square miles) of Earth's land surface is covered in ice including glaciers, ice caps, and the ice sheets of Greenland and Antarctica, most of which are retreating as a consequence of increased atmospheric CO2. Glaciers are teeming with life and supraglacial snow and ice surfaces are often red due to blooms of photoautotrophic algae. Recent evidence suggests the red pigmentation, secondary carotenoids produced in part to thrive under high irradiation, lowers albedo and accelerates melt. However, there are relatively few studies that report the productivity of snow algae communities and the parameters that constrain their growth on snow and ice surfaces. Here, we demonstrate that snow algae primary productivity can be stimulated by the addition of inorganic carbon. We found an increase in light-dependent carbon assimilation in snow algae microcosms amended with increasing amounts of inorganic carbon. Our snow algae communities were dominated by typical cosmopolitan snow algae species recovered from Alpine and Arctic environments. The climate feedbacks necessary to enter and exit glacial/interglacial oscillations are poorly understood. Evidence and models agree that global Snowball events are accompanied by changes in atmospheric CO2 with increasing CO2 necessary for entering periods of interglacial time. Our results demonstrate a positive feedback between increased CO2 and snow algal productivity and presumably growth. With the recent call for bio-albedo effects to be considered in climate models, our results underscore the need for robust climate models to include feedbacks between supraglacial primary productivity, albedo, and atmospheric CO2.

An electrical bio-chip to transfer and detect electromagnetic stimulation on the cells based on vertically aligned carbon nanotubes.

Science.gov (United States)

Rafizadeh-Tafti, Saeed; Haqiqatkhah, Mohammad Hossein; Saviz, Mehrdad; Janmaleki, Mohsen; Faraji Dana, Reza; Zanganeh, Somayeh; Abdolahad, Mohammad

2017-01-01

A highly sensitive impedimetric bio-chip based on vertically aligned multiwall carbon nanotubes (VAMWCNTs), was applied in direct interaction with lung cancer cells. Our tool provided both inducing and monitoring the bioelectrical changes in the cells initiated by electromagnetic (EM) wave stimulation. EM wave of 940MHz frequency with different intensities was used. Here, wave ablation might accumulate electrical charge on the tips of nanotubes penetrated into cell's membrane. The charge might induce ionic exchanges into the cell and cause alterations in electrical states of the membrane. Transmembrane electrostatic/dynamic states would be strongly affected due to such exchanges. Our novel modality was that, the cells' vitality changes caused by charge inductions were electrically detected with the same nanotubes in the architecture of electrodes for impedance measurement. The responses of the sensor were confirmed by electron and florescent microscopy images as well as biological assays. In summation, our method provided an effective biochip for enhancing and detecting external EM stimulation on the cells useful for future diagnostic and therapeutic applications, such as wave-guided drug-resistance breakage. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of Field-Emission Electron Gun from Carbon Nanotubes

CERN Document Server

Hozumi, Y

2004-01-01

Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2

Electronic properties of pristine and modified single-walled carbon nanotubes

International Nuclear Information System (INIS)

Kharlamova, M V

2013-01-01

The current status of research on the electronic properties of filled single-walled carbon nanotubes (SWCNTs) is reviewed. SWCNT atomic structure and electronic properties are described, and their correlation is discussed. Methods for modifying the electronic properties of SWCNTs are considered. SWCNT filling materials are systematized. Experimental and theoretical data on the electronic properties of filled SWCNTs are analyzed. Possible application areas for filled SWCNTs are explored. (reviews of topical problems)

Focused-electron-beam-induced processing (FEBIP) for emerging applications in carbon nanoelectronics

International Nuclear Information System (INIS)

Fedorov, Andrei G.; Kim, Songkil; Henry, Mathias; Kulkarni, Dhaval; Tsukruk, Vladimir V.

2014-01-01

Focused-electron-beam-induced processing (FEBIP), a resist-free additive nanomanufacturing technique, is an actively researched method for ''direct-write'' processing of a wide range of structural and functional nanomaterials, with high degree of spatial and time-domain control. This article attempts to critically assess the FEBIP capabilities and unique value proposition in the context of processing of electronics materials, with a particular emphasis on emerging carbon (i.e., based on graphene and carbon nanotubes) devices and interconnect structures. One of the major hurdles in advancing the carbon-based electronic materials and device fabrication is a disjoint nature of various processing steps involved in making a functional device from the precursor graphene/CNT materials. Not only this multi-step sequence severely limits the throughput and increases the cost, but also dramatically reduces the processing reproducibility and negatively impacts the quality because of possible between-the-step contamination, especially for impurity-susceptible materials such as graphene. The FEBIP provides a unique opportunity to address many challenges of carbon nanoelectronics, especially when it is employed as part of an integrated processing environment based on multiple ''beams'' of energetic particles, including electrons, photons, and molecules. This avenue is promising from the applications' prospective, as such a multi-functional (electron/photon/molecule beam) enables one to define shapes (patterning), form structures (deposition/etching), and modify (cleaning/doping/annealing) properties with locally resolved control on nanoscale using the same tool without ever changing the processing environment. It thus will have a direct positive impact on enhancing functionality, improving quality and reducing fabrication costs for electronic devices, based on both conventional CMOS and emerging carbon (CNT/graphene) materials. (orig.)

Nanofabrication and Nanopatterning of Carbon Nanomaterials for Flexible Electronics

Science.gov (United States)

Ding, Junjun

Stretchable electrodes have increasingly drawn attention as a vital component for flexible electronic devices. Carbon nanomaterials such as graphene and carbon nanotubes (CNTs) exhibit properties such as high mechanical flexibility and strength, optical transparency, and electrical conductivity which are naturally required for stretchable electrodes. Graphene growth, nanopatterning, and transfer processes are important steps to use graphene as flexible electrodes. However, advances in the large-area nanofabrication and nanopatterning of carbon nanomaterials such as graphene are necessary to realize the full potential of this technology. In particular, laser interference lithography (LIL), a fast and low cost large-area nanoscale patterning technique, shows tremendous promise for the patterning of graphene and other nanostructures for numerous applications. First, it was demonstrated that large-area nanopatterning and the transfer of chemical vapor deposition (CVD) grown graphene via LIL and plasma etching provide a reliable method to provide large area nanoengineered graphene on various target substrates. Then, to improve the electrode performance under large strain (naturally CVD grown graphene sheet will crack at tensile strains larger than 1%), a corrugated graphene structure on PDMS was designed, fabricated, and tested, with experimental results indicating that this approach successfully allows the graphene sheets to withstand cyclic tensile strains up to 15%. Lastly, to further enhance the performance of carbon-based stretchable electrodes, an approach was developed which coupled graphene and vertically aligned CNT (VACNT) on a flexible PDMS substrate. Characterization of the graphene-VACNT hybrid shows high electrical conductivity and durability through 50 cycles of loading up to 100% tensile strain. While flexible electronics promise tremendous advances in important technological areas such as healthcare, sensing, energy, and wearable electronics, continued

Superhard sp2–sp3 hybrid carbon allotropes with tunable electronic properties

Directory of Open Access Journals (Sweden)

Meng Hu

2016-05-01

Full Text Available Four sp2–sp3 hybrid carbon allotropes are proposed on the basis of first principles calculations. These four carbon allotropes are energetically more favorable than graphite under suitable pressure conditions. They can be assembled from graphite through intralayer wrinkling and interlayer buckling, which is similar to the formation of diamond from graphite. For one of the sp2–sp3 hybrid carbon allotropes, mC24, the electron diffraction patterns match these of i-carbon, which is synthesized from shock-compressed graphite (H. Hirai and K. Kondo, Science, 1991, 253, 772. The allotropes exhibit tunable electronic characteristics from metallic to semiconductive with band gaps comparable to those of silicon allotropes. They are all superhard materials with Vickers hardness values comparable to that of cubic BN. The sp2–sp3 hybrid carbon allotroes are promising materials for photovoltaic electronic devices, and abrasive and grinding tools.

The electronic fine structure of 4-nitrophenyl functionalized single-walled carbon nanotubes

International Nuclear Information System (INIS)

Chakraborty, Amit K; Coleman, Karl S; Dhanak, Vinod R

2009-01-01

Controlling the electronic structure of carbon nanotubes (CNTs) is of great importance to various CNT based applications. Herein the electronic fine structure of single-walled carbon nanotube films modified with 4-nitrophenyl groups, produced following reaction with 4-nitrobenzenediazonium tetrafluoroborate, was investigated for the first time. Various techniques such as x-ray and ultra-violet photoelectron spectroscopy, and near edge x-ray absorption fine structure studies were used to explore the electronic structure, and the results were compared with the measured electrical resistances. A reduction in number of the π electronic states in the valence band consistent with the increased resistance of the functionalized nanotube films was observed.

Carbon K-shell excitation in small molecules by high-resolution electron impact

International Nuclear Information System (INIS)

Tronc, M.; King, G.C.; Read, F.H.

1979-01-01

The excitation of 1s carbon electrons has been observed in C0, CH 4 , CF4, C0 2 , COS, C 2 H 2 and C 2 H 4 by means of the electron energy-loss technique with high resolution (70 meV in the 300 eV excitation energy range) and at an incident electron energy of 1.5 keV. The energies, widths and vibrational structures of excited states corresponding to the promotion of 1s carbon electrons to unoccupied valence and Rydberg orbitals have been obtained. The validity of the equivalent-core model, and the role of resonances caused by potential barriers, are discussed. (author)

Monte Carlo calculation of secondary electron emission from carbon-surface by obliquely incident particles

International Nuclear Information System (INIS)

Ohya, Kaoru; Kawata, Jun; Mori, Ichiro

1990-01-01

Incidence angle dependences of secondary electron emission from a carbon surface by low energy electron and hydrogen atom are calculated using Monte Carlo simulations on the kinetic emission model. The calculation shows very small increase or rather decrease of the secondary electron yield with oblique incidence. It is explained in terms of not only multiple elastic collisions of incident particles with the carbon atoms but also small penetration depth of the particles comparable with the escape depth of secondary electrons. In addition, the two types of secondary electron emission are distinguished by using the secondary electron yield statistics; one is the emission due to trapped particles in the carbon, and the other is that due to backscattered particles. The high-yield component of the statistics on oblique incidence is more suppressed than those on normal incidence. (author)

Recent advances in molecular electronics based on carbon nanotubes.

Science.gov (United States)

Bourgoin, Jean-Philippe; Campidelli, Stéphane; Chenevier, Pascale; Derycke, Vincent; Filoramo, Arianna; Goffman, Marcelo F

2010-01-01

Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: (i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, (ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and (iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field.

An electrical bio-chip to transfer and detect electromagnetic stimulation on the cells based on vertically aligned carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Rafizadeh-Tafti, Saeed [Nanoelectronic Center of Excellence, Thin Film and Nanoelectronic Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of); Nano Bio Electronic Devices Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of); Haqiqatkhah, Mohammad Hossein [Center of Excellence on Applied Electromagnetic Systems, School of Electrical & Computer Engineering, University of Tehran, P.O. Box 14395-515, North Kargar Avenue, Tehran (Iran, Islamic Republic of); Saviz, Mehrdad [Antenna Laboratory, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, North Kargar Avenue, Tehran (Iran, Islamic Republic of); Janmaleki, Mohsen [Medical Nanotechnology and Tissue Engineering Research Center, Shahid Beheshti University of Medical Sciences, P.O. Box 1985717443, Tehran (Iran, Islamic Republic of); Faraji Dana, Reza [Center of Excellence on Applied Electromagnetic Systems, School of Electrical & Computer Engineering, University of Tehran, P.O. Box 14395-515, North Kargar Avenue, Tehran (Iran, Islamic Republic of); Zanganeh, Somayeh [Nanoelectronic Center of Excellence, Thin Film and Nanoelectronic Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of); Nano Bio Electronic Devices Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of); Abdolahad, Mohammad, E-mail: m.abdolahad@ut.ac.ir [Nanoelectronic Center of Excellence, Thin Film and Nanoelectronic Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of); Nano Bio Electronic Devices Lab, School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395/515, Tehran (Iran, Islamic Republic of)

2017-01-01

A highly sensitive impedimetric bio-chip based on vertically aligned multiwall carbon nanotubes (VAMWCNTs), was applied in direct interaction with lung cancer cells. Our tool provided both inducing and monitoring the bioelectrical changes in the cells initiated by electromagnetic (EM) wave stimulation. EM wave of 940 MHz frequency with different intensities was used. Here, wave ablation might accumulate electrical charge on the tips of nanotubes penetrated into cell's membrane. The charge might induce ionic exchanges into the cell and cause alterations in electrical states of the membrane. Transmembrane electrostatic/dynamic states would be strongly affected due to such exchanges. Our novel modality was that, the cells' vitality changes caused by charge inductions were electrically detected with the same nanotubes in the architecture of electrodes for impedance measurement. The responses of the sensor were confirmed by electron and florescent microscopy images as well as biological assays. In summation, our method provided an effective biochip for enhancing and detecting external EM stimulation on the cells useful for future diagnostic and therapeutic applications, such as wave-guided drug-resistance breakage. - Highlights: • A CNT-chip is fabricated to stimulate cancer cells by electromagnetic wave. • Wave induced charges accumulation on the tip of CNTs penetrated into cells. • Transmembrane electrostatic states would be strongly affected due to such exchanges. • The cells' vitality changes could be happened and electrically detected with the same chip.

Promoting Interspecies Electron Transfer with Biochar

Science.gov (United States)

Chen, Shanshan; Rotaru, Amelia-Elena; Shrestha, Pravin Malla; Malvankar, Nikhil S.; Liu, Fanghua; Fan, Wei; Nevin, Kelly P.; Lovley, Derek R.

2014-01-01

Biochar, a charcoal-like product of the incomplete combustion of organic materials, is an increasingly popular soil amendment designed to improve soil fertility. We investigated the possibility that biochar could promote direct interspecies electron transfer (DIET) in a manner similar to that previously reported for granular activated carbon (GAC). Although the biochars investigated were 1000 times less conductive than GAC, they stimulated DIET in co-cultures of Geobacter metallireducens with Geobacter sulfurreducens or Methanosarcina barkeri in which ethanol was the electron donor. Cells were attached to the biochar, yet not in close contact, suggesting that electrons were likely conducted through the biochar, rather than biological electrical connections. The finding that biochar can stimulate DIET may be an important consideration when amending soils with biochar and can help explain why biochar may enhance methane production from organic wastes under anaerobic conditions. PMID:24846283

Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

DEFF Research Database (Denmark)

Tsukamoto, Sumiko; Murray, Andrew; Ankjærgaard, Christina

2010-01-01

electron concentration in the conduction band. In this study, TR-OSE and time-resolved optically stimulated luminescence (TR-OSL) were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 °C after beta...... irradiation and preheating to 280 °C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination...

Carbon Nano tube Composites for Electronic Packaging Applications: A Review

International Nuclear Information System (INIS)

Aryasomayajula, L.; Wolter, K.J.

2013-01-01

Composite engineering comprises of metal matrix composites. They have high strength-weight ratio, better stiffness, economical production, and ease of availability of raw materials. The discovery of carbon nano tubes has opened new possibilities to face challenges better. Carbon Nano tubes are known for their high mechanical strength, excellent thermal and electrical properties. Recent research has made progress in fabricating carbon nano tube metal matrix and polymer-based composites. The methods of fabrication of these composites, their properties and possible applications restricted to the field of electronic packaging have been discussed in this paper. Experimental and theoretical calculations have shown improved mechanical and physical properties like tensile stress, toughness, and improved electrical and thermal properties. They have also demonstrated the ease of production of the composites and their adaptability as one can tailor their properties as per the requirement. This paper reviews work reported on fabricating and characterizing carbon- nano tube-based metal matrix and polymer composites. The focus of this paper is mainly to review the importance of these composites in the field of electronics packaging.

Stability and electronic structure of carbon capsules with superior gas storage properties: A theoretical study

International Nuclear Information System (INIS)

Manna, Arun K.; Pati, Swapan K.

2013-01-01

Highlights: • Stability and electronic structure of various carbon capsules are studied. • Effects of capsule’s sizes on electronic and optical properties are explored. • Changes in cohesive and formation energy and electronic gap are discussed. • Capsule’s gas storage propensity is addressed using DFT and ab initio MD. • Capsule’s optical absorptions are discussed with and without stored gas molecules. - Abstract: Structures, electronic and optical properties of carbon nanocapsules of varying sizes (length and diameter) are studied using first-principles density functional theory. Based on calculated cohesive energy, formation energy, electronic gap and extent of orbital delocalization, we examine structural stability and changes in low-energy physics of these carbon capsules. We find that both cohesive and formation energy decrease with increase in capsule’s sizes, indicating their greater structural rigidity and favorable formation feasibility. The electronic gap also decreases with increase in capsule’s sizes due to the larger electronic delocalization. The simulated optical absorption spectra show lowering of low-energy peak positions with increase in the capsule’s dimensions, consistent with the reduction in electronic gap. Additionally, we also provide an estimate of gas storage capacity for the larger carbon capsule (C 460 ) considered. We find 7.69 wt.% and 28.08 wt.% storage propensity for hydrogen and carbon dioxide gases, respectively, which clearly suggests their potential use as light storage materials

Carbon nanotube on Si(001): structural and electronic properties

International Nuclear Information System (INIS)

Orellana, W.; Fazzio, A.; Miwa, R.W.

2003-01-01

Full text: The promising nanoscale technology based on carbon nanotubes has attracted much attention due to the unique electronic, chemical and mechanical properties of the nanotubes. Single-wall carbon nanotubes (SWCNs) provide an ideal atomically uniform one dimensional (1D) conductors, having a strong electronic confinement around its circumference, which can be retained up to room temperature[1]. This interesting property may lead one to consider SWCNs as 1D conductors for the development of nanoscale electronic devices. In this work the structural and electronic properties of the contact between a metallic (6,6) SWCN adsorbed on a silicon (001) surface are studied from first-principles total-energy calculations. We consider two adsorption sites for the tube on the Si(001) surface: on the top of the Si-dimer rows and on the surface 'trench' between two consecutive dimer rows. Our results show a chemical bond between the nanotube and Si(001) when the tube is located along the 'trench', which corresponds to the only bound structure. We find a binding energy per tube length of 0.21 eV/angstrom. We also verified that the binding energy depends on the rotation of the tube. Typically, a rotation of 15 deg can reduce the binding energy up to 0.07 eV/angstrom. Our calculated electronic properties indicate that the most stable structure shows a subband associated to the tube/surface bond that cross the Fermi level. This result indicates an enhanced metallic behavior along the tube/surface contact characterizing a 1D quantum wire. The charge transfer between the Si surface and the tube is also discussed. [1] Z. Yao, C. Dekker, and P. Avouris in Carbon Nanotubes, M. S. Dresselhaus, G. Dresselhaus, and P. Avouris Eds., (Springer, Berlin 2001), p. 147. (author)

Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

International Nuclear Information System (INIS)

Majidi, R.; Ghafoori Tabrizi, K.; Jalili, S.

2009-01-01

The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

Energy Technology Data Exchange (ETDEWEB)

Majidi, R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Ghafoori Tabrizi, K., E-mail: K-TABRIZI@sbu.ac.i [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Jalili, S. [Department of Chemistry, K.N. Toosi University of Technology, Tehran 16315-1618 (Iran, Islamic Republic of)

2009-11-01

The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

Substrate dependence of electron-stimulated O - yields from dissociative electron attachment to physisorbed O2

Science.gov (United States)

Huels, M. A.; Parenteau, L.; Sanche, L.

1994-03-01

We present measurements of O- electron stimulated desorption yields obtained under identical experimental conditions from 0.15 monolayers (ML) of O2 deposited onto disordered substrates consisting of 4 ML of either Kr, Xe, C2H6, C2H4, N2O, CH3Cl, or H2O, all condensed on Pt (polycrystalline). The resulting O- yield functions, for incident electron energies below 20 eV, are compared to that obtained from the O2/Kr solid; this allows us to assess the order of magnitude effects of the local substrate environment on dissociative electron attachment (DEA) via the 2Πu and gas phase forbidden 2Σ+g,u resonances of O-2. We note that, in addition to electron energy losses in the substrate prior to DEA to O2 and post-dissociation interactions of the O- with the substrate molecules, charge or energy transfer from the O-2 transient anion to a substrate molecule, and capture of the incident electron into a dissociative anion resonance of the substrate molecule may contribute to a reduced O- yield from the physisorbed O2. In the case of O2 deposited on amorphous ice, we find that the O- signal from DEA to O2 is completely absent for electron energies below 14 eV; we attribute this to a complete quenching of the dissociative O-2(2Πu, 2Σ+) resonances by the adjacent water molecules.

Low-Energy Electron-Stimulated Luminescence of Thin H20 and D20 Layers on Pt(111)

International Nuclear Information System (INIS)

Petrik, Nikolay G.; Kimmel, Greg A.

2005-01-01

The electron-stimulated luminescence (ESL) from amorphous solid water and crystalline ice films deposited on Pt(111) at 100 K is investigated as a function of the film thickness, incident electron energy (5 ? 1000 eV), isotopic composition, and film structure. The ESL emission spectrum has a characteristic double-peaked shape that has been attributed to a transition between a superexcited state ( ) and the dissociative, first excited state ( ) in water: Comparing the electron-stimulated luminescence and O2 electron-stimulated desorption (ESD) yields versus incident electron energy, we find the ESL threshold blue-shifted from the O2 ESD threshold by ∼3 eV, which is close to the center of the emission spectrum near 400 nm and supports the assignment for the ESL. For thin films, radiative and non-radiative interactions with the substrate tend to quench the luminescence. The luminescence yield increases with coverage since the interactions with the substrate become less important. The ESL yield from D2O is ∼ 4 times higher than from H2O. Using layered films of H2O and D2O, this sizable isotopic effect on the ESL is exploited to spatially profile the luminescence emission within the ASW films. These experiments show that most of the luminescence is emitted from within the penetration depth of the incident electron. However, the results depend on the order of the isotopes in the film, and this asymmetry can be modeled by assuming some migration of the excited states within the film. The ESL is very sensitive to defects and structural changes in solid water, and the emission yield is significantly higher from amorphous films than from crystalline ice

On the interplay of morphology and electronic conductivity of rotationally spun carbon fiber mats

Science.gov (United States)

Opitz, Martin; Go, Dennis; Lott, Philipp; Müller, Sandra; Stollenwerk, Jochen; Kuehne, Alexander J. C.; Roling, Bernhard

2017-09-01

Carbon-based materials are used as electrode materials in a wide range of electrochemical applications, e.g., in batteries, supercapacitors, and fuel cells. For these applications, the electronic conductivity of the materials plays an important role. Currently, porous carbon materials with complex morphologies and hierarchical pore structures are in the focus of research. The complex morphologies influence the electronic transport and may lead to an anisotropic electronic conductivity. In this paper, we unravel the influence of the morphology of rotationally spun carbon fiber mats on their electronic conductivity. By combining experiments with finite-element simulations, we compare and evaluate different electrode setups for conductivity measurements. While the "bar-type method" with two parallel electrodes on the same face of the sample yields information about the intrinsic conductivity of the carbon fibers, the "parallel-plate method" with two electrodes on opposite faces gives information about the electronic transport orthogonal to the faces. Results obtained for the van-der-Pauw method suggest that this method is not well suited for understanding morphology-transport relations in these materials.

Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

NARCIS (Netherlands)

de Jonge, N.; van Druten, N.J.

2003-01-01

Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

Carbon nanotube based pressure sensor for flexible electronics

International Nuclear Information System (INIS)

So, Hye-Mi; Sim, Jin Woo; Kwon, Jinhyeong; Yun, Jongju; Baik, Seunghyun; Chang, Won Seok

2013-01-01

Highlights: • The electromechanical change of vertically aligned carbon nanotubes. • Fabrication of CNT field-effect transistor on flexible substrate. • CNT based FET integrated active pressure sensor. • The integrated device yields an increase in the source-drain current under pressure. - Abstract: A pressure sensor was developed based on an arrangement of vertically aligned carbon nanotubes (VACNTs) supported by a polydimethylsiloxane (PDMS) matrix. The VACNTs embedded in the PDMS matrix were structurally flexible and provided repeated sensing operation due to the high elasticities of both the polymer and the carbon nanotubes (CNTs). The conductance increased in the presence of a loading pressure, which compressed the material and induced contact between neighboring CNTs, thereby producing a dense current path and better CNT/metal contacts. To achieve flexible functional electronics, VACNTs based pressure sensor was integrated with field-effect transistor, which is fabricated using sprayed semiconducting carbon nanotubes on plastic substrate

Carbon nanotube based pressure sensor for flexible electronics

Energy Technology Data Exchange (ETDEWEB)

So, Hye-Mi [Department of Nano Mechanics, Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343 (Korea, Republic of); Sim, Jin Woo [Advanced Nano Technology Ltd., Seoul 132-710 (Korea, Republic of); Kwon, Jinhyeong [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); Yun, Jongju; Baik, Seunghyun [SKKU Advanced Institute of Nanotechnology (SAINT), Department of Energy Science and School of Mechanical Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746 (Korea, Republic of); Chang, Won Seok, E-mail: paul@kimm.re.kr [Department of Nano Mechanics, Nanomechanical Systems Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343 (Korea, Republic of)

2013-12-15

Highlights: • The electromechanical change of vertically aligned carbon nanotubes. • Fabrication of CNT field-effect transistor on flexible substrate. • CNT based FET integrated active pressure sensor. • The integrated device yields an increase in the source-drain current under pressure. - Abstract: A pressure sensor was developed based on an arrangement of vertically aligned carbon nanotubes (VACNTs) supported by a polydimethylsiloxane (PDMS) matrix. The VACNTs embedded in the PDMS matrix were structurally flexible and provided repeated sensing operation due to the high elasticities of both the polymer and the carbon nanotubes (CNTs). The conductance increased in the presence of a loading pressure, which compressed the material and induced contact between neighboring CNTs, thereby producing a dense current path and better CNT/metal contacts. To achieve flexible functional electronics, VACNTs based pressure sensor was integrated with field-effect transistor, which is fabricated using sprayed semiconducting carbon nanotubes on plastic substrate.

Electronic and optical properties of finite carbon nanotubes in an electric field

International Nuclear Information System (INIS)

Chen, R B; Lee, C H; Chang, C P; Lin, M F

2007-01-01

The effects, caused by the geometric structure and an electric field (E), on the electronic and optical properties of quasi-zero-dimensional finite carbon nanotubes are explored by employing the tight-binding model coupled with curvature effects. Electronic properties (state energies, symmetry of electronic states, energy spacing and state degeneracy) are significantly affected by the magnitude and the direction of the electric field and the geometric structure (radius, length and chirality). The electric field, by lowering the symmetry of finite carbon nanotubes, modifies the electronic properties. Thus, the optical excitation spectra, excited by electric polarization parallel to the nanotube axis, exhibit rich delta-function-like peaks, which reveal the characteristics of the electronic properties. Therefore it follows that geometric structure and E influence the low-energy absorption spectra, i.e. the change of frequency of the first peak, the alternation of the peak height and the production of the new peaks. There are more absorption peaks when E is oriented closer to the cross-section plane. Moreover, the very complicated optical absorption spectra are characteristic for the individual chiral carbon nanotube due to its specific geometric structure. Above all, the predicted absorption spectra and the associated electronic properties could be verified by optical measurements

Three phase carbon EOS model with electronic excitation

International Nuclear Information System (INIS)

van Thiel, M.; Ree, F.H.; Grover, R.

1987-07-01

A simple and rapid way for computing EOS data of multiphase solids with a liquid phase is described with emphasis on carbon. The method uses a scaling model for the liquid phase and includes a provision for electronic effects. The free energy minimum determines the stable phase

Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

International Nuclear Information System (INIS)

Lee, Jeonyoon; Stein, Itai Y.; Devoe, Mackenzie E.; Lewis, Diana J.; Lachman, Noa; Buschhorn, Samuel T.; Wardle, Brian L.; Kessler, Seth S.

2015-01-01

Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network

Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeonyoon; Stein, Itai Y. [Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Devoe, Mackenzie E. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Lewis, Diana J.; Lachman, Noa; Buschhorn, Samuel T.; Wardle, Brian L., E-mail: wardle@mit.edu [Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Kessler, Seth S. [Metis Design Corporation, 205 Portland St., Boston, Massachusetts 02114 (United States)

2015-02-02

Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.

From chemolithoautotrophs to electrolithoautotrophs: CO2 fixation by Fe(II)-oxidizing bacteria coupled with direct uptake of electrons from solid electron sources.

Science.gov (United States)

Ishii, Takumi; Kawaichi, Satoshi; Nakagawa, Hirotaka; Hashimoto, Kazuhito; Nakamura, Ryuhei

2015-01-01

At deep-sea vent systems, hydrothermal emissions rich in reductive chemicals replace solar energy as fuels to support microbial carbon assimilation. Until recently, all the microbial components at vent systems have been assumed to be fostered by the primary production of chemolithoautotrophs; however, both the laboratory and on-site studies demonstrated electrical current generation at vent systems and have suggested that a portion of microbial carbon assimilation is stimulated by the direct uptake of electrons from electrically conductive minerals. Here we show that chemolithoautotrophic Fe(II)-oxidizing bacterium, Acidithiobacillus ferrooxidans, switches the electron source for carbon assimilation from diffusible Fe(2+) ions to an electrode under the condition that electrical current is the only source of energy and electrons. Site-specific marking of a cytochrome aa3 complex (aa3 complex) and a cytochrome bc1 complex (bc1 complex) in viable cells demonstrated that the electrons taken directly from an electrode are used for O2 reduction via a down-hill pathway, which generates proton motive force that is used for pushing the electrons to NAD(+) through a bc1 complex. Activation of carbon dioxide fixation by a direct electron uptake was also confirmed by the clear potential dependency of cell growth. These results reveal a previously unknown bioenergetic versatility of Fe(II)-oxidizing bacteria to use solid electron sources and will help with understanding carbon assimilation of microbial components living in electronically conductive chimney habitats.

Electron emission induced modifications in amorphous tetrahedral diamondlike carbon

International Nuclear Information System (INIS)

Mercer, T.W.; DiNardo, N.J.; Rothman, J.B.; Siegal, M.P.; Friedmann, T.A.; Martinez-Miranda, L.J.

1998-01-01

The cold-cathode electron emission properties of amorphous tetrahedral diamondlike carbon are promising for flat-panel display and vacuum microelectronics technologies. The onset of electron emission is, typically, preceded by open-quotes conditioningclose quotes where the material is stressed by an applied electric field. To simulate conditioning and assess its effect, we combined the spatially localized field and current of a scanning tunneling microscope tip with high-spatial-resolution characterization. Scanning force microscopy shows that conditioning alters surface morphology and electronic structure. Spatially resolved electron-energy-loss spectroscopy indicates that the predominant bonding configuration changes from predominantly fourfold to threefold coordination. copyright 1998 American Institute of Physics

Carbon Nanotube Conditioning: Ab Initio Simulations of the Effect of Interwall Interaction, Defects And Doping on the Electronic Properties of Carbon Nanotubes

Science.gov (United States)

Castillo, Matias Soto

Using carbon nanotubes for electrical conduction applications at the macroscale has been shown to be a difficult task for some time now, mainly, due to defects and impurities present, and lack of uniform electronic properties in synthesized carbon nanotube bundles. Some researchers have suggested that growing only metallic armchair nanotubes and arranging them with an ideal contact length could lead to the ultimate electrical conductivity; however, such recipe presents too high of a cost to pay. A different route is to learn to manage the defects, impurities, and the electronic properties of carbon nanotubes present in bundles grown by current state-of-the-art reactors, so that the electrical conduction of a bundle or even wire may be enhanced. In our work, we have used first-principles density functional theory calculations to study the effect of interwall interaction, defects and doping on the electronic structure of metallic, semi-metal and semiconducting single- and double-walled carbon nanotubes in order to gain a clear picture of their properties. The electronic band gap for a range of zigzag single-walled carbon nanotubes with chiral indices (5,0) - (30,0) was obtained. Their properties were used as a stepping stone in the study of the interwall interaction in double-walled carbon nanotubes, from which it was found that the electronic band gap depends on the type of inner and outer tubes, average diameter, and interwall distance. The effect of vacancy defects was also studied for a range of single-walled carbon nanotubes. It was found that the electronic band gap is reduced for the entire range of zigzag carbon nanotubes, even at vacancy defects concentrations of less than 1%. Finally, interaction potentials obtained via first-principles calculations were generalized by developing mathematical models for the purpose of running simulations at a larger length scale using molecular dynamics of the adsorption doping of diatomic iodine. An ideal adsorption site

Carbon nanotubes--electronic/electrochemical properties and application for nanoelectronics and photonics.

Science.gov (United States)

Sgobba, Vito; Guldi, Dirk M

2009-01-01

The fundamental chemical, redox, electrochemical, photoelectrochemical, optical and optoelectronic features of carbon nanotubes are surveyed with particular emphasis on the most relevant applications as electron donor/electron acceptor or as electron conductor/hole conductor materials, in solutions and in the solid state. Methods that aim at p- and n-doping as a means to favor hole or electron injection/transport are covered as well (critical review, 208 references).

Modifying the electronic and optical properties of carbon nanotubes

Science.gov (United States)

Kinder, Jesse M.

The intrinsic electronic and optical properties of carbon nanotubes make them promising candidates for circuit elements and LEDs in nanoscale devices. However, applied fields and interactions with the environment can modify these intrinsic properties. This dissertation is a theoretical study of perturbations to an ideal carbon nanotube. It illustrates how transport and optical properties of carbon nanotubes can be adversely affected or intentionally modified by the local environment. The dissertation is divided into three parts. Part I analyzes the effect of a transverse electric field on the single-electron energy spectrum of semiconducting carbon nanotubes. Part II analyzes the effect of the local environment on selection rules and decay pathways relevant to dark excitons. Part III is a series of 26 appendices. Two different models for a transverse electric field are introduced in Part I. The first is a uniform field perpendicular to the nanotube axis. This model suggests the field has little effect on the band gap until it exceeds a critical value that can be tuned with strain or a magnetic field. The second model is a transverse field localized to a small region along the nanotube axis. The field creates a pair of exponentially localized bound states but has no effect on the band gap for particle transport. Part II explores the physics of dark excitons in carbon nanotubes. Two model calculations illustrate the effect of the local environment on allowed optical transitions and nonradiative recombination pathways. The first model illustrates the role of inversion symmetry in the optical spectrum. Broken inversion symmetry may explain low-lying peaks in the exciton spectrum of boron nitride nanotubes and localized photoemission around impurities and interfaces in carbon nanotubes. The second model in Part II suggests that free charge carriers can mediate an efficient nonradiative decay process for dark excitons in carbon nanotubes. The appendices in Part III

Structural, electronic and magnetic properties of carbon doped boron nitride nanowire: Ab initio study

Energy Technology Data Exchange (ETDEWEB)

Jalilian, Jaafar, E-mail: JaafarJalilian@gmail.com [Young Researchers and Elite Club, Kermanshah Br anch, Islamic Azad University, P.O. Box: 6718997551, Kermanshah (Iran, Islamic Republic of); Kanjouri, Faramarz, E-mail: kanjouri@khu.ac.ir [Physics Department, Faculty of Science, Kharazmi University, University Square, P.O. Box: 3197937551, Karaj (Iran, Islamic Republic of)

2016-11-15

Using spin-polarized density functional theory calculations, we demonstrated that carbon doped boron nitride nanowire (C-doped BNNW) has diverse electronic and magnetic properties depending on position of carbon atoms and their percentages. Our results show that only when one carbon atom is situated on the edge of the nanowire, C-doped BNNW is transformed into half-metal. The calculated electronic structure of the C-doped BNNW suggests that doping carbon can induce localized edge states around the Fermi level, and the interaction among localized edge states leads to semiconductor to half-metal transition. Overall, the bond reconstruction causes of appearance of different electronic behavior such as semiconducting, half-metallicity, nonmagnetic metallic, and ferromagnetic metallic characters. The formation energy of the system shows that when a C atom is doped on surface boron site, system is more stable than the other positions of carbon impurity. Our calculations show that C-doped BNNW may offer unique opportunities for developing nanoscale spintronic materials.

Identification of the site where the electron transfer chain of plant mitochondria is stimulated by electrostatic charge screening.

NARCIS (Netherlands)

Krab, K.; Wagner, M.J.; Wagner, A.M.; Moller, I.M.

2000-01-01

Modular kinetic analysis was used to determine the sites in plant mitochondria where charge-screening stimulates the rate of electron transfer from external NAD(P)H to oxygen. In mitochondria isolated from potato (Solanum tuberosum L.) tuber callus, stimulation of the rate of oxygen uptake was

Electron spectroscopy of rubber and resin-based composites containing 2D carbon

International Nuclear Information System (INIS)

Kaciulis, S.; Mezzi, A.; Balijepalli, S.K.; Lavorgna, M.; Xia, H.S.

2015-01-01

Composite materials with 2D carbon (graphene and/or single wall carbon nanotubes) are very promising due to their extraordinary electrical and mechanical properties. Graphene and natural rubber composites, which may be used for the gaskets or sealants, were prepared by ultrasonically assisted latex-mixing exfoliation and in-situ reduction process, with two vulcanization approaches: roll-mixing and hot-pressing. Also the resin-based composites, filled with micro-particles of Ag and graphene or carbon nanotubes, have been studied. The standards for the compositional characterization of these materials still are not established. In addition to the mostly used techniques, such as Raman spectroscopy and electron microscopy, also Auger electron spectroscopy can be employed for the identification of graphene. In this study, the shape of C KVV peak, excited by electron beam and X-ray photons, has been investigated in different composite materials containing graphene and carbon nanotubes. A spectroscopic method for 2D carbon recognition, based on the D x parameter which is determined from C KVV signal excited by X-ray photons, was proposed and verified. Even a small content of graphene in different types of composites was sufficient for this recognition due to the dominating presence of graphene on the surface of composites. - Highlights: • Chemical composition of the rubber composites was determined by XPS. • Auger spectrum of carbon was used for graphene identification in composites. • Small content of graphene was sufficient for its recognition from the D parameter

Electron spectroscopy of rubber and resin-based composites containing 2D carbon

Energy Technology Data Exchange (ETDEWEB)

Kaciulis, S., E-mail: saulius.kaciulis@ismn.cnr.it [Institute for the Study of Nanostructured Materials, ISMN-CNR, P.O. Box 10, Monterotondo Stazione, 00015 Roma (Italy); Mezzi, A.; Balijepalli, S.K. [Institute for the Study of Nanostructured Materials, ISMN-CNR, P.O. Box 10, Monterotondo Stazione, 00015 Roma (Italy); Lavorgna, M. [Institute of Polymers, Composites and Biomaterials, IPCB-CNR, P.le Fermi, 80055 Napoli (Italy); Xia, H.S. [State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, 610065 Sichuan (China)

2015-04-30

Composite materials with 2D carbon (graphene and/or single wall carbon nanotubes) are very promising due to their extraordinary electrical and mechanical properties. Graphene and natural rubber composites, which may be used for the gaskets or sealants, were prepared by ultrasonically assisted latex-mixing exfoliation and in-situ reduction process, with two vulcanization approaches: roll-mixing and hot-pressing. Also the resin-based composites, filled with micro-particles of Ag and graphene or carbon nanotubes, have been studied. The standards for the compositional characterization of these materials still are not established. In addition to the mostly used techniques, such as Raman spectroscopy and electron microscopy, also Auger electron spectroscopy can be employed for the identification of graphene. In this study, the shape of C KVV peak, excited by electron beam and X-ray photons, has been investigated in different composite materials containing graphene and carbon nanotubes. A spectroscopic method for 2D carbon recognition, based on the D{sub x} parameter which is determined from C KVV signal excited by X-ray photons, was proposed and verified. Even a small content of graphene in different types of composites was sufficient for this recognition due to the dominating presence of graphene on the surface of composites. - Highlights: • Chemical composition of the rubber composites was determined by XPS. • Auger spectrum of carbon was used for graphene identification in composites. • Small content of graphene was sufficient for its recognition from the D parameter.

Structural, electronic and optical properties of carbon nitride

Energy Technology Data Exchange (ETDEWEB)

Cohen, M L [California Univ., Berkeley (United States). Dept. of Physics

1996-05-01

Carbon nitride was proposed as a superhard material and a structural prototype, {beta}-C{sub 3}N{sub 4}, was examined using several theoretical models. Some reports claiming experimental verifications have been made recently. The current status of the theory and experiment is reviewed, and a detailed discussion is presented of calculations of the electronic and optical properties of this material. These calculations predict that {beta}-C{sub 3}N{sub 4} will have a minimum gap which is indirect at 6.4{+-}0.5 eV. A discussion of the possibility of carbon nitride nanotubes is also presented. (orig.)

Bulk Cutting of Carbon Nanotubes Using Electron Beam Irradiation

Science.gov (United States)

Ziegler, Kirk J. (Inventor); Rauwald, Urs (Inventor); Hauge, Robert H. (Inventor); Schmidt, Howard K. (Inventor); Smalley, Richard E. (Inventor); Kittrell, W. Carter (Inventor); Gu, Zhenning (Inventor)

2013-01-01

According to some embodiments, the present invention provides a method for attaining short carbon nanotubes utilizing electron beam irradiation, for example, of a carbon nanotube sample. The sample may be pretreated, for example by oxonation. The pretreatment may introduce defects to the sidewalls of the nanotubes. The method is shown to produces nanotubes with a distribution of lengths, with the majority of lengths shorter than 100 tun. Further, the median length of the nanotubes is between about 20 nm and about 100 nm.

A Carbon Nanotube Electron Source Based Ionization Vacuum Gauge

Energy Technology Data Exchange (ETDEWEB)

Changkun Dong; Ganapati Myneni

2003-10-01

The results of fabrication and performance of an ionization vacuum gauge using a carbon nanotube (CNT) electron source are presented. The electron source was constructed with multi-wall nanotubes (MWNT), which were grown using thermal chemical vapor deposition (CVD) process. The electron emission of the source was stable in vacuum pressure up to 10-7 Torr, which is better than the metal field emitters. The measurement linearity of the gauge was better than {+-}10% from 10-6 to 10-10 Torr. The gauge sensitivity of 4 Torr-1 was achieved under 50 {micro}A electron emission in nitrogen. The gauge is expected to find applications in vacuum measurements from 10-7 Torr to below 10-11 Torr.

Improvement of carbon fiber surface properties using electron beam irradiation

International Nuclear Information System (INIS)

Pino, E.S.; Machado, L.D.B.; Giovedi, C.

2007-01-01

Carbon fiber-reinforced advance composites have been used for structural applications, mainly on account of their mechanical properties. The main factor for a good mechanical performance of carbon fiber-reinforced composite is the interfacial interaction between its components, which are carbon fiber and polymeric matrix. The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite. EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests. Experimental results showed that EB irradiation improved the tensile strength of carbon fiber samples. The maximum value in tensile strength was reached using doses of about 250 kGy. After breakage, the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated car- bon fibers were evaluated. SEM micrographs showed modifications on the carbon fiber surface. (authors)

Electronic and transport properties of a carbon-atom chain in the core of semiconducting carbon nanotubes

International Nuclear Information System (INIS)

Chen Jiangwei; Yang Linfeng; Yang Huatong; Dong Jinming

2003-01-01

Using the tight-binding calculations, we have studied electronic and transport properties of the semiconducting single-walled carbon nanotubes (SSWNTs) doped by a chain of carbon-atoms, which can be well controlled by density of the encapsulated carbon atoms. When it is lower, weak coupling between the chain atoms and the tube produces flat bands near the Fermi level, which means a great possibility of superconductivity and ferromagnetism for the combined system. The weak coupling also leads to a significant conductance at the Fermi level, which is contributed by both of the tube and the encapsulated carbon-atom chain. Increasing density of the chain carbon atoms, the flat bands near the Fermi level disappear, and the current may be carried only by the carbon-atom chain, thus making the system become an ideal one-dimensional quantum wire with its conducting chain enclosed by a SWNT insulator

Electron paramagnetic resonance investigations of carbon-doped β rhombohedral boron

International Nuclear Information System (INIS)

Gercke, U.; Siems, C.-D.

1979-01-01

Electron paramagnetic resonance (EPR) measurements at 9 and 35 GHz on polycrystalline β rhombohedral boron with various carbon contents resulted in partly resolved absorption spectra. At 300 K the spin density ratio of two lines (called D and E) showed a linear increase with the carbon content. This ratio is temperature dependent. The lines D and E are photo-EPR active with different quantum efficiencies at various temperatures. (Auth.)

Single-walled carbon nanotube networks for flexible and printed electronics

International Nuclear Information System (INIS)

Zaumseil, Jana

2015-01-01

Networks of single-walled carbon nanotubes (SWNTs) can be processed from solution and have excellent mechanical properties. They are highly flexible and stretchable. Depending on the type of nanotubes (semiconducting or metallic) they can be used as replacements for metal or transparent conductive oxide electrodes or as semiconducting layers for field-effect transistors (FETs) with high carrier mobilities. They are thus competitive alternatives to other solution-processable materials for flexible and printed electronics. This review introduces the basic properties of SWNTs, current methods for dispersion and separation of metallic and semiconducting SWNTs and techniques to deposit and pattern dense networks from dispersion. Recent examples of applications of carbon nanotubes as conductors and semiconductors in (opto-)electronic devices and integrated circuits will be discussed. (paper)

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

Energy Technology Data Exchange (ETDEWEB)

Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q.J. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Chen, X. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Ostrikov, K., E-mail: kostya.ostrikov@csiro.au [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2011-09-22

Highlights: > A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. > The carbon nanotubes are later treated with nitrogen plasmas. > The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. > A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 {mu}A/cm{sup 2}) achieved at a low applied field (3.50 V/{mu}m) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

International Nuclear Information System (INIS)

Wang, B.B.; Cheng, Q.J.; Chen, X.; Ostrikov, K.

2011-01-01

Highlights: → A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. → The carbon nanotubes are later treated with nitrogen plasmas. → The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. → A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 μA/cm 2 ) achieved at a low applied field (3.50 V/μm) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

Nanotubes on Display: How Carbon Nanotubes Can Be Integrated into Electronic Displays

KAUST Repository

Opatkiewicz, Justin; LeMieux, Melburne C.; Bao, Zhenan

2010-01-01

Random networks of single-walled carbon nanotubes show promise for use in the field of flexible electronics. Nanotube networks have been difficult to utilize because of the mixture of electronic types synthesized when grown. A variety of separation

Role of lattice structure and low temperature resistivity in fast-electron-beam filamentation in carbon

International Nuclear Information System (INIS)

Dance, R J; Butler, N M H; Gray, R J; MacLellan, D A; Rusby, D R; Xu, H; Neely, D; McKenna, P; Scott, G G; Robinson, A P L; Zielbauer, B; Bagnoud, V; Desjarlais, M P

2016-01-01

The influence of low temperature (eV to tens-of-eV) electrical resistivity on the onset of the filamentation instability in fast-electron transport is investigated in targets comprising of layers of ordered (diamond) and disordered (vitreous) carbon. It is shown experimentally and numerically that the thickness of the disordered carbon layer influences the degree of filamentation of the fast-electron beam. Strong filamentation is produced if the thickness is of the order of 60 μm or greater, for an electron distribution driven by a sub-picosecond, mid-10 20 Wcm −2 laser pulse. It is shown that the position of the vitreous carbon layer relative to the fast-electron source (where the beam current density and background temperature are highest) does not have a strong effect because the resistive filamentation growth rate is high in disordered carbon over a wide range of temperatures up to the Spitzer regime. (paper)

Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

International Nuclear Information System (INIS)

Haghighi, Behzad; Tabrizi, Mahmoud Amouzadeh

2011-01-01

Highlights: → A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. → A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. → The apparent electron transfer rate constant was measured to be 5.27 s -1 . → A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E o ') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k s ) was calculated to be 5.27 s -1 . The dependence of E o ' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

Energy Technology Data Exchange (ETDEWEB)

Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Tabrizi, Mahmoud Amouzadeh [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of)

2011-11-30

Highlights: > A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. > A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. > The apparent electron transfer rate constant was measured to be 5.27 s{sup -1}. > A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E{sup o}') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k{sub s}) was calculated to be 5.27 s{sup -1}. The dependence of E{sup o}' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

Observation of Electronic Raman Scattering in Metallic Carbon Nanotubes

Czech Academy of Sciences Publication Activity Database

Farhat, H.; Berciaud, S.; Kalbáč, Martin; Saito, R.; Heinz, T. F.; Dresselhaus, M. S.; Kong, J.

2011-01-01

Roč. 107, č. 15 (2011), s. 157401 ISSN 0031-9007 R&D Projects: GA MŠk ME09060 Institutional research plan: CEZ:AV0Z40400503 Keywords : spectroscopy * electronic Raman scattering * metallic carbon nanotubes Subject RIV: CG - Electrochemistry Impact factor: 7.370, year: 2011

Improvement of carbon fibre surface properties using electron beam irradiation

International Nuclear Information System (INIS)

Eddy Segura Pino; Luci Diva Brocardo Machado; Claudia Giovedi

2006-01-01

Carbon fiber-reinforced advance composites have been used for structural applications, mainly due to their mechanical properties, and additional features such as high strength-to-weight ratio, stiffness-to-weight ratio, corrosion resistance and wear properties. The main factor for a good mechanical performance of carbon fiber-reinforced composite is the interfacial interaction between the components that are fiber and polymeric matrix. The greatest challenge is to improve adhesion between components having elasticity modulus which differ by orders of magnitude and furthermore they are immiscible in each other. Another important factor is the sizing material on the carbon fiber, which protects the carbon fiber filaments and must be compatible with the matrix material in order to improve the adhesion process. The interaction of ionizing radiation from electron beam can induce in the irradiated material the formation of very active centers and free radicals. Further evolution of these active species can significantly modify structure and properties not only in the irradiated polymeric matrix but also on the fiber surface. So that, fiber and matrix play an important role in the production of chemical bonds, which promote better adhesion between both materials improving the composite mechanical performance. The aim of this work was to improve the surface properties of the carbon fiber surface using ionizing radiation from an electron beam in order to obtain improvement of the adhesion properties in the resulted composite. Commercial carbon fiber roving of high tensile strength with 12 000 filaments named 12 k, and sizing material of epoxy resin modified by ester groups was studied. EB irradiation has been carried out at the Institute for Nuclear and Energy Research (IPEN) facilities using a 1.5 MeV 37.5 kW Dynamitron electron accelerator model JOB-188. Rovings of carbon fibers with 1.78 g cm -3 density and 0.13 mm thickness were irradiated with 0.555 MeV, 6.43 mA and

Superhard sp{sup 2}–sp{sup 3} hybrid carbon allotropes with tunable electronic properties

Energy Technology Data Exchange (ETDEWEB)

Hu, Meng; Ma, Mengdong; Zhao, Zhisheng; Yu, Dongli; He, Julong, E-mail: hjl@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2016-05-15

Four sp{sup 2}–sp{sup 3} hybrid carbon allotropes are proposed on the basis of first principles calculations. These four carbon allotropes are energetically more favorable than graphite under suitable pressure conditions. They can be assembled from graphite through intralayer wrinkling and interlayer buckling, which is similar to the formation of diamond from graphite. For one of the sp{sup 2}–sp{sup 3} hybrid carbon allotropes, mC24, the electron diffraction patterns match these of i-carbon, which is synthesized from shock-compressed graphite (H. Hirai and K. Kondo, Science, 1991, 253, 772). The allotropes exhibit tunable electronic characteristics from metallic to semiconductive with band gaps comparable to those of silicon allotropes. They are all superhard materials with Vickers hardness values comparable to that of cubic BN. The sp{sup 2}–sp{sup 3} hybrid carbon allotroes are promising materials for photovoltaic electronic devices, and abrasive and grinding tools.

Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron-hole recombination

International Nuclear Information System (INIS)

Carpene, E; Mancini, E; Dallera, C; Schwen, D; Ronning, C; Silvestri, S De

2007-01-01

We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electron-phonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electron-hole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electron-hole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors

A graphene oxide-carbon nanotube grid for high-resolution transmission electron microscopy of nanomaterials

International Nuclear Information System (INIS)

Zhang Lina; Zhang Haoxu; Zhou Ruifeng; Chen Zhuo; Li Qunqing; Fan Shoushan; Jiang Kaili; Ge Guanglu; Liu Renxiao

2011-01-01

A novel grid for use in transmission electron microscopy is developed. The supporting film of the grid is composed of thin graphene oxide films overlying a super-aligned carbon nanotube network. The composite film combines the advantages of graphene oxide and carbon nanotube networks and has the following properties: it is ultra-thin, it has a large flat and smooth effective supporting area with a homogeneous amorphous appearance, high stability, and good conductivity. The graphene oxide-carbon nanotube grid has a distinct advantage when characterizing the fine structure of a mass of nanomaterials over conventional amorphous carbon grids. Clear high-resolution transmission electron microscopy images of various nanomaterials are obtained easily using the new grids.

Direct detection of neutral metal atoms in electron-stimulated desorption: Al from CH3O/Al(111) - velocity distribution and absolute yield

International Nuclear Information System (INIS)

Whitten, J.E.; Young, C.E.; Pellin, M.J.; Gruen, D.M.; Jones, P.L.

1994-01-01

Electron-stimulated desorption of neutral aluminum from the system CH 3 O/Al(111) has been directly monitored via quasiresonant photoionization with 193 nm excimer laser light and confirmed by two-step resonant ionization, utilizing the Al 3d 2 D manifold. Velocity distribution measurements for the neutral Al peak at ∼ 800 m/s for 1 keV incident electron energy. An absolute yield of 3.2 x 10 -6 Al atoms/electron was determined by comparison with sputtering measurements in the same apparatus. This is the first observation of electron-stimulated metal desorption from adsorbate-covered metallic surfaces

Evaluating Origin of Electron Traps in Tris(8-hydroxyquinoline) Aluminum Thin Films using Thermally Stimulated Current Technique

OpenAIRE

Matsushima, Toshinori; Adachi, Chihaya

2008-01-01

We measured the energy distributions and concentrations of electron traps in O_2-unexposed and O_2-exposed tris(8-hydroxyquinoline) aluminum (Alq_3) films using a thermally stimulated current (TSC) technique to investigate how doping O_2 molecules in Alq_3 films affect the films' electron trap and electron transport characteristics. The results of our TSC studies revealed that Alq_3 films have an electron trap distribution with peak depths ranging from 0.075 to 0.1 eV and peak widths ranging ...

Vertical electric field stimulated neural cell functionality on porous amorphous carbon electrodes.

Science.gov (United States)

Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

2013-12-01

We demonstrate the efficacy of amorphous macroporous carbon substrates as electrodes to support neuronal cell proliferation and differentiation in electric field mediated culture conditions. The electric field was applied perpendicular to carbon substrate electrode, while growing mouse neuroblastoma (N2a) cells in vitro. The placement of the second electrode outside of the cell culture medium allows the investigation of cell response to electric field without the concurrent complexities of submerged electrodes such as potentially toxic electrode reactions, electro-kinetic flows and charge transfer (electrical current) in the cell medium. The macroporous carbon electrodes are uniquely characterized by a higher specific charge storage capacity (0.2 mC/cm(2)) and low impedance (3.3 kΩ at 1 kHz). The optimal window of electric field stimulation for better cell viability and neurite outgrowth is established. When a uniform or a gradient electric field was applied perpendicular to the amorphous carbon substrate, it was found that the N2a cell viability and neurite length were higher at low electric field strengths (≤ 2.5 V/cm) compared to that measured without an applied field (0 V/cm). While the cell viability was assessed by two complementary biochemical assays (MTT and LDH), the differentiation was studied by indirect immunostaining. Overall, the results of the present study unambiguously establish the uniform/gradient vertical electric field based culture protocol to either enhance or to restrict neurite outgrowth respectively at lower or higher field strengths, when neuroblastoma cells are cultured on porous glassy carbon electrodes having a desired combination of electrochemical properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

Carbon nanotube conditioning: ab initio simulations of the effect of defects and doping on the electronic properties of carbon nanotube systems.

Science.gov (United States)

Soto, Matias; Barrera, Enrique

Using carbon nanotubes for electrical conduction applications at the macroscale has proven to be a difficult task, mainly, due to defects and impurities present, and lack of uniform electronic properties in synthesized carbon nanotube bundles. Some researchers have suggested that growing only metallic armchair nanotubes and arranging them with an ideal contact length could lead to the ultimate electrical conductivity; however, such recipe presents too high of a cost to pay. A different route and the topic of this work is to learn to manage the defects, impurities, and the electronic properties of carbon nanotubes present, so that the electrical conduction of a bundle or even wire may be enhanced. We used density functional theory calculations to study the effect of defects and doping on the electronic structure of metallic, semi-metal and semiconducting carbon nanotubes in order to gain a clear picture of their properties. Additionally, using dopants to increase the conductance across a junction between two carbon nanotubes was studied for different configurations. Finally, interaction potentials obtained via first-principles calculations were generalized by developing mathematical models for the purpose of running simulations at a larger length scale using molecular dynamics. Partial funding was received from CONACyT Scholarship 314419.

Giant modulation of the electronic band gap of carbon nanotubes by dielectric screening

NARCIS (Netherlands)

Aspitarte, Lee; McCulley, Daniel R.; Bertoni, Andrea; Island, J.O.; Ostermann, Marvin; Rontani, Massimo; Steele, G.A.; Minot, Ethan D.

2017-01-01

Carbon nanotubes (CNTs) are a promising material for high-performance electronics beyond silicon. But unlike silicon, the nature of the transport band gap in CNTs is not fully understood. The transport gap in CNTs is predicted to be strongly driven by electron-electron (e-e) interactions and

Electronic Properties of Disclinations in Carbon Nanostructures

International Nuclear Information System (INIS)

Sitenko, Yu.A.; Vlasii, N.D.; Sitenko, Yu.A.; Vlasii, N.D.

2007-01-01

The recent synthesis of strictly two-dimensional atomic crystals (monolayers of carbon atoms) is promising a wealth of new phenomena and possible applications in technology and industry. Such materials are characterized by the Dirac-type spectrum of quasiparticle excitations, yielding a unique example of the truly two-dimensional 'relativistic' electronic system which, in the presence of disclinations, possesses rather unusual properties. We consider the influence of disclinations on densities of states and induced vacuum quantum numbers in grapheme

Low Secondary Electron Yield Carbon Coatings for Electron Cloud Mitigation in Modern Particle Accelerators

CERN Document Server

Yin Vallgren, Christina; Taborelli, Mauro

2011-01-01

In order to upgrade the Large Hadron Collider (LHC) performance to be oriented towards higher energies and higher intensities in the future, a series of improvements of the existing LHC injectors is planned to take place over the next few years. Electron cloud effects are expected to be enhanced and play a central role in limiting the performance of the machines of the CERN complex. Electron cloud phenomena in beam pipes are based on electron multiplication and can be sufficiently suppressed if the Secondary Electron Yield (SEY) of the surface of the beam pipes is lower than unity. The goal of this work is to find and study a thin film coating with reliably low initial Secondary Electron Yield (SEY), which does not require bake-out or conditioning in situ with photons, is robust again air exposure and can easily be applied in the beam pipes of accelerators. In this work, amorphous carbon (a-C) thin films have been prepared by DC magnetron sputtering for electron cloud mitigation and antimultipactor applicatio...

In situ measurements and transmission electron microscopy of carbon nanotube field-effect transistors

International Nuclear Information System (INIS)

Kim, Taekyung; Kim, Seongwon; Olson, Eric; Zuo Jianmin

2008-01-01

We present the design and operation of a transmission electron microscopy (TEM)-compatible carbon nanotube (CNT) field-effect transistor (FET). The device is configured with microfabricated slits, which allows direct observation of CNTs in a FET using TEM and measurement of electrical transport while inside the TEM. As demonstrations of the device architecture, two examples are presented. The first example is an in situ electrical transport measurement of a bundle of carbon nanotubes. The second example is a study of electron beam radiation effect on CNT bundles using a 200 keV electron beam. In situ electrical transport measurement during the beam irradiation shows a signature of wall- or tube-breakdown. Stepwise current drops were observed when a high intensity electron beam was used to cut individual CNT bundles in a device with multiple bundles

Evaluations of carbon nanotube field emitters for electron microscopy

Science.gov (United States)

Nakahara, Hitoshi; Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi

2009-11-01

Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I- V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6×109 A/m 2 sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

Electronic structure and transport of a carbon chain between graphene nanoribbon leads

International Nuclear Information System (INIS)

Zhang, G P; Fang, X W; Yao, Y X; Wang, C Z; Ho, K M; Ding, Z J

2011-01-01

The electronic structure and transport property of a carbon chain between two graphene nanoribbon leads are studied using an ab initio tight-binding (TB) model and Landauer's formalism combined with a non-equilibrium Green's function. The TB Hamiltonian and overlap matrices are extracted from first-principles density functional calculations through the quasi-atomic minimal basis orbital scheme. The accuracy of the TB model is demonstrated by comparing the electronic structure from the TB model with that from first-principles density functional theory. The results of electronic transport on a carbon atomic chain connected to armchair and zigzag graphene ribbon leads, such as different transport characters near the Fermi level and at most one quantized conductance, reveal the effect of the electronic structure of the leads and the scattering from the atomic chain. In addition, bond length alternation and an interesting transmission resonance are observed in the atomic chain connected to zigzag graphene ribbon leads. Our approach provides a promising route to quantitative investigation of both the electronic structure and transport property of large systems.

In situ transmission electron microscopy of individual carbon nanotetrahedron/ribbon structures in bending

Energy Technology Data Exchange (ETDEWEB)

Kohno, Hideo, E-mail: kohno.hideo@kochi-tech.ac.jp [School of Environmental Science and Engineering, Kochi University of Technology, Kami, Kochi 782-8502 (Japan); Masuda, Yusuke [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

2015-05-11

When the direction of flattening of a carbon nanotube changes during growth mediated by a metal nanoparticle, a carbon nanotetrahedron is formed in the middle of the carbon nanoribbon. We report the bending properties of the carbon nanotetrahedron/nanoribbon structure using a micro-manipulator system in a transmission electron microscope. In many cases, bending occurs at an edge of the carbon nanotetrahedron. No significant change is observed in the tetrahedron's shape during bending, and the bending is reversible and repeatable. Our results show that the carbon nanotetrahedron/nanoribbon structure has good durability against mechanical bending.

Performance of a carbon nanotube field emission electron gun

Science.gov (United States)

Getty, Stephanie A.; King, Todd T.; Bis, Rachael A.; Jones, Hollis H.; Herrero, Federico; Lynch, Bernard A.; Roman, Patrick; Mahaffy, Paul

2007-04-01

A cold cathode field emission electron gun (e-gun) based on a patterned carbon nanotube (CNT) film has been fabricated for use in a miniaturized reflectron time-of-flight mass spectrometer (RTOF MS), with future applications in other charged particle spectrometers, and performance of the CNT e-gun has been evaluated. A thermionic electron gun has also been fabricated and evaluated in parallel and its performance is used as a benchmark in the evaluation of our CNT e-gun. Implications for future improvements and integration into the RTOF MS are discussed.

Electronic structures and magnetism for carbon doped CdSe: Modified Becke–Johnson density functional calculations

Energy Technology Data Exchange (ETDEWEB)

Fan, S.W., E-mail: fansw1129@126.com; Song, T.; Huang, X.N.; Yang, L.; Ding, L.J.; Pan, L.Q.

2016-09-15

Utilizing the full potential linearized augment plane wave method, the electronic structures and magnetism for carbon doped CdSe are investigated. Calculations show carbon substituting selenium could induce CdSe to be a diluted magnetic semiconductor. Single carbon dopant could induce 2.00 μ{sub B} magnetic moment. Electronic structures show the long-range ferromagnetic coupling mainly originates from the p–d exchange-like p–p coupling interaction. Positive chemical pair interactions indicate carbon dopants would form homogeneous distribution in CdSe host. The formation energy implies the non-equilibrium fabricated technology is necessary during the samples fabricated. - Highlights: • The C{sub Se} defects could induce the CdSe to be typical diluted magnetic semiconductor. • Electronic structures show ferromagnetism come from p-d exchange-like p-p coupling. • Chemical pair interactions indicate C{sub Se} prefer homogenous distribution in CdSe host.

Electron transfer dynamics of triphenylamine dyes bound to TiO2 nanoparticles from femtosecond stimulated Raman spectroscopy

KAUST Repository

Hoffman, David P.; Lee, Olivia P.; Millstone, Jill E.; Chen, Mark S.; Su, Timothy A.; Creelman, Mark; Frechet, Jean; Mathies, Richard A.

2013-01-01

Interfacial electron transfer between sensitizers and semiconducting nanoparticles is a crucial yet poorly understood process. To address this problem, we have used transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS

Necessity of electrically conductive pili for methanogenesis with magnetite stimulation

Directory of Open Access Journals (Sweden)

Oumei Wang

2018-03-01

Full Text Available Background Magnetite-mediated direct interspecies electron transfer (DIET between Geobacter and Methanosarcina species is increasingly being invoked to explain magnetite stimulation of methane production in anaerobic soils and sediments. Although magnetite-mediated DIET has been documented in defined co-cultures reducing fumarate or nitrate as the electron acceptor, the effects of magnetite have only been inferred in methanogenic systems. Methods Concentrations of methane and organic acid were analysed with a gas chromatograph and high-performance liquid chromatography, respectively. The concentration of HCl-extractable Fe(II was determined by the ferrozine method. The association of the defined co-cultures of G. metallireducens and M. barkeri with magnetite was observed with transmission electron micrographs. Results Magnetite stimulated ethanol metabolism and methane production in defined co-cultures of G. metallireducens and M. barkeri; however, magnetite did not promote methane production in co-cultures initiated with a culture of G. metallireducens that could not produce electrically conductive pili (e-pili, unlike the conductive carbon materials that facilitate DIET in the absence of e-pili. Transmission electron microscopy revealed that G. metallireducens and M. barkeri were closely associated when magnetite was present, as previously observed in G. metallireducens/G. sulfurreducens co-cultures. These results show that magnetite can promote DIET between Geobacter and Methanosarcina species, but not as a substitute for e-pili, and probably functions to facilitate electron transfer from the e-pili to Methanosarcina. Conclusion In summary, the e-pili are necessary for the stimulation of not only G. metallireducens/G. sulfurreducens, but also methanogenic G. metallireducens/M. barkeri co-cultures with magnetite.

Low energy electron stimulated desorption from DNA films dosed with oxygen

Energy Technology Data Exchange (ETDEWEB)

Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Cloutier, Pierre; Massey, Sylvain; Sanche, Leon [Groupe en sciences des radiations, Faculte de medecine et des sciences de la sante, Universite de Sherbrooke, Sherbrooke, Quebec J1H 5N4 (Canada)

2012-06-21

Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O{sub 2}. The OH{sup -} desorption yields increase markedly with exposure to O{sub 2} at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O{sup -}, attributable to dissociative electron attachment to trapped O{sub 2} molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O{sub 2} shows that this surprising increase in OH{sup -} desorption, at elevated temperatures, arises from the reaction of O{sub 2} with damaged DNA sites. These results thus appear to be a manifestation of the so-called 'oxygen fixation' effect, well known in radiobiology.

Evaluations of carbon nanotube field emitters for electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Nakahara, Hitoshi, E-mail: nakahara@nagoya-u.jp [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2009-11-30

Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I-V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6x10{sup 9} A/m{sup 2} sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

Carbon Electrode-Molecule Junctions: A Reliable Platform for Molecular Electronics.

Science.gov (United States)

Jia, Chuancheng; Ma, Bangjun; Xin, Na; Guo, Xuefeng

2015-09-15

The development of reliable approaches to integrate individual or a small collection of molecules into electrical nanocircuits, often termed "molecular electronics", is currently a research focus because it can not only overcome the increasing difficulties and fundamental limitations of miniaturization of current silicon-based electronic devices, but can also enable us to probe and understand the intrinsic properties of materials at the atomic- and/or molecular-length scale. This development might also lead to direct observation of novel effects and fundamental discovery of physical phenomena that are not accessible by traditional materials or approaches. Therefore, researchers from a variety of backgrounds have been devoting great effort to this objective, which has started to move beyond simple descriptions of charge transport and branch out in different directions, reflecting the interdisciplinarity. This Account exemplifies our ongoing interest and great effort in developing efficient lithographic methodologies capable of creating molecular electronic devices through the combination of top-down micro/nanofabrication with bottom-up molecular assembly. These devices use nanogapped carbon nanomaterials (such as single-walled carbon nanotubes (SWCNTs) and graphene), with a particular focus on graphene, as point contacts formed by electron beam lithography and precise oxygen plasma etching. Through robust amide linkages, functional molecular bridges terminated with diamine moieties are covalently wired into the carboxylic acid-functionalized nanogaps to form stable carbon electrode-molecule junctions with desired functionalities. At the macroscopic level, to improve the contact interface between electrodes and organic semiconductors and lower Schottky barriers, we used SWCNTs and graphene as efficient electrodes to explore the intrinsic properties of organic thin films, and then build functional high-performance organic nanotransistors with ultrahigh responsivities

Bright luminance from silicon dioxide film with carbon nanotube electron beam exposure

Energy Technology Data Exchange (ETDEWEB)

Lee, Su Woong; Hong, Ji Hwan; Kang, Jung Su; Callixte, Shikili; Park, Kyu Chang, E-mail: kyupark@khu.ac.kr

2016-02-15

We observed the bright bluish-white luminescence with naked eye from carbon nanotube electron beam exposed silicon dioxide (SiO{sub 2}) thin film on Si substrate. The luminescence shows a peak intensity at 2.7 eV (460 nm) with wide spread up to 600 nm after the C-beam exposed on SiO{sub 2} thin film. The C-beam exposure system is composed of carbon nanotube emitters as electron beam source. The brightness strongly depend on the exposure condition. Luminescence characteristic was optimized by C-beam adjustment to observe with the naked eye. The cause of luminescence in the C-beam exposed SiO{sub 2} thin film is analyzed by CL microscopy, FT-IR, AFM and ellipsometer. Decrease of Si–O bonding was observed after C-beam exposure, and this reveals that oxygen deficient defects which are irradiation-sensitive cause 2.7 eV peak of luminescence. - Highlights: • We observed bright luminescence for SiO{sub 2} thin film with naked eye by carbon nanotube electron beam (C-beam) exposure technique. • The bright luminance from C-beam exposed SiO{sub 2} film will open novel silicon optoelectronics.

Investigation of new superhard carbon allotropes with promising electronic properties

Energy Technology Data Exchange (ETDEWEB)

Kvashnina, Yulia A.; Kvashnin, Alexander G. [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutsky Lane, 141700 Dolgoprudny (Russian Federation); Sorokin, Pavel B., E-mail: psorokin@iph.krasn.ru [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutsky Lane, 141700 Dolgoprudny (Russian Federation); Emanuel Institute of Biochemical Physics of RAS, 4 Kosigina St., Moscow 119334 (Russian Federation)

2013-11-14

During the systematic search for a new superhard carbon allotrope, we predicted three structures with promising physical properties. Our electronic structure calculations show that these materials have a semiconducting band gap and a high carrier mobility comparable with diamond. The simulated x-ray diffraction patterns of the proposed materials are in a good agreement with the experimental X-ray spectra. Evaluated phase transition pressures from graphite to the new proposed carbon phases are smaller than 25 GPa and close to the experimental values.

Investigation of industrial-scale carbon dioxide reduction using pulsed electron beams

Energy Technology Data Exchange (ETDEWEB)

Petrov, G. M.; Apruzese, J. P.; Petrova, Tz. B.; Wolford, M. F. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375-5346 (United States)

2016-03-14

Carbon dioxide is the most important greenhouse gas contributing to global warming. To help mitigate increasing CO{sub 2} concentrations, we investigate a method of carbon dioxide reduction using high-power electron beams, which can be used on an industrial scale. A series of experiments are conducted in which the reduction of CO{sub 2} is measured for different gas compositions and power deposition rates. An electron beam deposition model is applied to compute reduction rates of CO{sub 2} and energy cost for breaking a CO{sub 2} molecule in flue gas and pure carbon dioxide at atmospheric pressure. For flue gas consisting of 82% N{sub 2}, 6% O{sub 2}, and 12% CO{sub 2}, the calculated energy cost is 85 eV per molecule. In order to dissociate 50% of the CO{sub 2} molecules, beam energy density deposition on the order of 20 J/cm{sup 3} is required. Electron beam irradiation of 12.6 liter gas volume containing 90% CO{sub 2} and 10% CH{sub 4} at beam energy density deposition of 4.2 J/cm{sup 3}, accumulated over 43 shots in a 20 min interval, reduced the CO{sub 2} concentration to 78%. Analogous experiments with a gas mixture containing 11.5% CO{sub 2}, 11.5% CH{sub 4}, and balance of Ar, reduced the CO{sub 2} concentration to below 11% with energy deposition 0.71 J/cm{sup 3}, accumulated over 10 shots in a 5 min interval. The experimental data and the theoretical predictions of CO{sub 2} reduction using pulsed electron beams are in agreement within the experimental error. Other techniques to enhance the removal of CO{sub 2} with pulsed electron beams are also explored, yielding new possible avenues of research.

Positron annihilation and thermally stimulated current of electron beam irradiated polyetheretherketone

Energy Technology Data Exchange (ETDEWEB)

Fujita, Shigetaka; Shinyama, Katsuyoshi; Baba, Makoto [Hachinohe Inst. of Tech., Hachinohe, Aomori (Japan); Suzuki, Takenori

1997-03-01

Positron lifetime measurements were applied to electron beam irradiated poly(ether-ether-ketone). The lifetime, {tau}{sub 3}, of the ortho-positronium of unirradiated and 5 MGy irradiated specimen became rapidly longer above about 150degC. {tau}{sub 3} of 50 MGy and 100 MGy irradiated specimen was shorter than that of unirradiated one. Thermally stimulated current (TSC) decreased with increasing the dose before voltage application. In the case of voltage application, a TSC peak appeared and the peak value decreased with increased the dose. The correlation between the results of positron annihilation and TSC was investigated. (author)

Flexible Carbon Aerogels

Directory of Open Access Journals (Sweden)

Marina Schwan

2016-09-01

Full Text Available Carbon aerogels are highly porous materials with a large inner surface area. Due to their high electrical conductivity they are excellent electrode materials in supercapacitors. Their brittleness, however, imposes certain limitations in terms of applicability. In that context, novel carbon aerogels with varying degree of flexibility have been developed. These highly porous, light aerogels are characterized by a high surface area and possess pore structures in the micrometer range, allowing for a reversible deformation of the aerogel network. A high ratio of pore size to particle size was found to be crucial for high flexibility. For dynamic microstructural analysis, compression tests were performed in-situ within a scanning electron microscope allowing us to directly visualize the microstructural flexibility of an aerogel. The flexible carbon aerogels were found to withstand between 15% and 30% of uniaxial compression in a reversible fashion. These findings might stimulate further research and new application fields directed towards flexible supercapacitors and batteries.

Nanoscale Soldering of Positioned Carbon Nanotubes using Highly Conductive Electron Beam Induced Gold Deposition

DEFF Research Database (Denmark)

Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina

2003-01-01

We have developed an in-situ method for controlled positioning of carbon nanotubes followed by highly conductive contacting of the nanotubes, using electron beam assisted deposition of gold. The positioning and soldering process takes place inside an Environmental Scanning Electron Microscope (E...... in a carbon matrix. Nanoscale soldering of multi-walled carbon nanotubes (MWNT) onto microelectrodes was achieved by deposition of a conducting gold line across a contact point between nanotube and electrode. The solderings were found to be mechanically stronger than the carbon nanotubes. We have positioned...... MWNTs to bridge the gap between two electrodes, and formed soldering bonds between the tube and each of the electrodes. All nanotube bridges showed ohmic resistances in the range 10-30 kΩ. We observed no increase in resistance after exposing the MWNT bridge to air for days....

Powering microbes with electricity: direct electron transfer from electrodes to microbes.

Science.gov (United States)

Lovley, Derek R

2011-02-01

The discovery of electrotrophs, microorganisms that can directly accept electrons from electrodes for the reduction of terminal electron acceptors, has spurred the investigation of a wide range of potential applications. To date, only a handful of pure cultures have been shown to be capable of electrotrophy, but this process has also been inferred in many studies with undefined consortia. Potential electron acceptors include: carbon dioxide, nitrate, metals, chlorinated compounds, organic acids, protons and oxygen. Direct electron transfer from electrodes to cells has many advantages over indirect electrical stimulation of microbial metabolism via electron shuttles or hydrogen production. Supplying electrons with electrodes for the bioremediation of chlorinated compounds, nitrate or toxic metals may be preferable to adding organic electron donors or hydrogen to the subsurface or bioreactors. The most transformative application of electrotrophy may be microbial electrosynthesis in which carbon dioxide and water are converted to multi-carbon organic compounds that are released extracellularly. Coupling photovoltaic technology with microbial electrosynthesis represents a novel photosynthesis strategy that avoids many of the drawbacks of biomass-based strategies for the production of transportation fuels and other organic chemicals. The mechanisms for direct electron transfer from electrodes to microorganisms warrant further investigation in order to optimize envisioned applications. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.

Ab initio density functional theory investigation of electronic properties of semiconducting single-walled carbon nanotube bundles

Science.gov (United States)

Moradian, Rostam; Behzad, Somayeh; Azadi, Sam

2008-09-01

By using ab initio density functional theory we investigated the structural and electronic properties of semiconducting (7, 0), (8, 0) and (10, 0) carbon nanotube bundles. The energetic and electronic evolutions of nanotubes in the bundling process are also studied. The effects of inter-tube coupling on the electronic dispersions of semiconducting carbon nanotube bundles are demonstrated. Our results show that the inter-tube coupling decreases the energy gap in semiconducting nanotubes. We found that bundles of (7, 0) and (8, 0) carbon nanotubes have metallic feature, while (10, 0) bundle is a semiconductor with an energy gap of 0.22 eV. To clarify our results the band structures of isolated and bundled nanotubes are compared.

Electronic sputtering by swift highly charged ions of nitrogen on amorphous carbon

International Nuclear Information System (INIS)

Caron, M.; Haranger, F.; Rothard, H.; Ban d'Etat, B.; Boduch, P.; Clouvas, A.; Potiriadis, C.; Neugebauer, R.; Jalowy, T.

2001-01-01

Electronic sputtering with heavy ions as a function of both electronic energy loss dE/dx and projectile charge state q was studied at the French heavy ion accelerator GANIL. Amorphous carbon (untreated, and sputter-cleaned and subsequently exposed to nitrogen) was irradiated with swift highly charged ions (Z=6-73, q=6-54, energy 6-13 MeV/u) in an ultrahigh vacuum scattering chamber. The fluence dependence of ion-induced electron yields allows to deduce a desorption cross-section σ which varies approximately as σ∼(dE/dx) 1.65 or σ∼q 3.3 for sputter-cleaned amorphous carbon exposed to nitrogen. This q dependence is close to the cubic charge dependence observed for the emission of H + secondary ions which are believed to be emitted from the very surface. However, the power law σ∼(dE/dx) 1.65 , related to the electronic energy loss gives the best empirical description. The dependence on dE/dx is close to a quadratic one thus rather pointing towards a thermal evaporation-like effect

Fractal Interfaces for Stimulating and Recording Neural Implants

Science.gov (United States)

Watterson, William James

From investigating movement in an insect to deciphering cognition in a human brain to treating Parkinson's disease, hearing loss, or even blindness, electronic implants are an essential tool for understanding the brain and treating neural diseases. Currently, the stimulating and recording resolution of these implants remains low. For instance, they can record all the neuron activity associated with movement in an insect, but are quite far from recording, at an individual neuron resolution, the large volumes of brain tissue associated with cognition. Likewise, there is remarkable success in the cochlear implant restoring hearing due to the relatively simple anatomy of the auditory nerves, but are failing to restore vision to the blind due to poor signal fidelity and transmission in stimulating the more complex anatomy of the visual nerves. The critically important research needed to improve the resolution of these implants is to optimize the neuron-electrode interface. This thesis explores geometrical and material modifications to both stimulating and recording electrodes which can improve the neuron-electrode interface. First, we introduce a fractal electrode geometry which radically improves the restored visual acuity achieved by retinal implants and leads to safe, long-term operation of the implant. Next, we demonstrate excellent neuron survival and neurite outgrowth on carbon nanotube electrodes, thus providing a safe biomaterial which forms a strong connection between the electrode and neurons. Additional preliminary evidence suggests carbon nanotubes patterned into a fractal geometry will provide further benefits in improving the electrode-neuron interface. Finally, we propose a novel implant based off field effect transistor technology which utilizes an interconnecting fractal network of semiconducting carbon nanotubes to record from thousands of neurons simutaneously at an individual neuron resolution. Taken together, these improvements have the potential to

Stimulation of neuronal neurite outgrowth using functionalized carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Matsumoto, K; Sato, C; Shimizu, N [Graduate School of Life Sciences, Toyo University, 1-1-1 Izumino, Itakura-machi, Ora-gun, Gunma 374-0193 (Japan); Naka, Y [Bio-Nano Electronics Research Center, Toyo University, 2100 Kujirai, Kawagoe-shi, Saitama 350-8585 (Japan); Whitby, R, E-mail: shimizu@toyonet.toyo.ac.jp [School of Pharmacy and Biomolecular Sciences, University of Brighton, Cockroft Building, Lewes Road, Brighton BN2 4GJ (United Kingdom)

2010-03-19

Low concentrations (0.11-1.7 {mu}g ml{sup -1}) of functionalized carbon nanotubes (CNTs), which are multi-walled CNTs modified by amino groups, when added with nerve growth factor (NGF), promoted outgrowth of neuronal neurites in dorsal root ganglion (DRG) neurons and rat pheochromocytoma cell line PC12h cells in culture media. The quantity of active extracellular signal-regulated kinase (ERK) was higher after the addition of both 0.85 {mu}g ml{sup -1} CNTs and NGF than that with NGF alone. CNTs increased the number of cells with neurite outgrowth in DRG neurons and PC12h cells after the inhibition of the ERK signaling pathway using a mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor. Active ERK proteins were detected in MEK inhibitor-treated neurons after the addition of CNTs to the culture medium. These results demonstrate that CNTs may stimulate neurite outgrowth by activation of the ERK signaling pathway. Thus, CNTs are biocompatible and are promising candidates for biological applications and devices.

Thermally stimulated luminescence and electron paramagnetic resonance studies on uranium doped calcium phosphate

CERN Document Server

Natarajan, V; Veeraraghavan, R; Sastry, M D

2003-01-01

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies on uranium doped calcium phosphate yielded mechanistic information on the observed glow peaks at 365, 410 and 450 K. TSL spectral studies of the glow peaks showed that UO sub 2 sup 2 sup + acts as the luminescent center. Electron paramagnetic resonance studies on gamma-irradiated samples revealed that the predominant radiation induced centers are H sup 0 , PO sub 4 sup 2 sup - , PO sub 3 sup 2 sup - and O sup - ion. Studies on the temperature dependence studies of the EPR spectra of samples annealed to different temperatures indicate the role of H sup 0 and PO sub 4 sup 2 sup - ions in the main glow peak at 410 K.

Trimodal nanoelectrode array for precise deep brain stimulation: prospects of a new technology based on carbon nanofiber arrays.

Science.gov (United States)

Li, J; Andrews, R J

2007-01-01

Although deep brain stimulation (DBS) has recently been shown to be effective for neurological disorders such as Parkinson's disease, there are many limitations of the current technology: the large size of current microelectrodes (approximately 1 mm diameter); the lack of monitoring of local brain electrical activity and neurotransmitters (e.g. dopamine in Parkinson's disease); the open-loop nature of the stimulation (i.e. not guided by brain electrochemical activity). Reducing the size of the monitoring and stimulating electrodes by orders of magnitude (to the size of neural elements) allows remarkable improvements in both monitoring (spatial resolution, temporal resolution, and sensitivity) and stimulation. Carbon nanofiber nanoelectrode technology offers the possibility of trimodal arrays (monitoring electrical activity, monitoring neurotransmitter levels, precise stimulation). DBS can then be guided by changes in brain electrical activity and/or neurotransmitter levels (i.e. closed-loop DBS). Here, we describe the basic manufacture and electrical characteristics of a prototype nanoelectrode array for DBS, as well as preliminary studies with electroconductive polymers necessary to optimize DBS in vivo. An approach such as the nanoelectrode array described here may offer a generic electrical-neural interface for use in various neural prostheses.

ITER Plasma at Electron Cyclotron Frequency Domain: Stimulated Raman Scattering off Gould-Trivelpiece Modes and Generation of Suprathermal Electrons and Energetic Ions

Science.gov (United States)

Stefan, V. Alexander

2011-04-01

Stimulated Raman scattering in the electron cyclotron frequency range of the X-Mode and O-Mode driver with the ITER plasma leads to the ``tail heating'' via the generation of suprathermal electrons and energetic ions. The scattering off Trivelpiece-Gould (T-G) modes is studied for the gyrotron frequency of 170GHz; X-Mode and O-Mode power of 24 MW CW; on-axis B-field of 10T. The synergy between the two-plasmon decay and Raman scattering is analyzed in reference to the bulk plasma heating. Supported in part by Nikola TESLA Labs, La Jolla, CA

Effect of Li Termination on the Electronic and Hydrogen Storage Properties of Linear Carbon Chains: A TAO-DFT Study

OpenAIRE

Seenithurai, Sonai; Chai, Jeng-Da

2017-01-01

Accurate prediction of the electronic and hydrogen storage properties of linear carbon chains (C n ) and Li-terminated linear carbon chains (Li2C n ), with n carbon atoms (n?=?5?10), has been very challenging for traditional electronic structure methods, due to the presence of strong static correlation effects. To meet the challenge, we study these properties using our newly developed thermally-assisted-occupation density functional theory (TAO-DFT), a very efficient electronic structure meth...

Nature of the concentration thresholds of europium atom yield from the oxidized tungsten surface under electron stimulated desorption

CERN Document Server

Davydov, S Y

2002-01-01

The nature of the electron-stimulated desorption (ESD) of the europium atoms by the E sub e irradiating electrons energies, equal to 50 and 80 eV, as well as peculiarities of the Eu atoms yield dependence on their concentration on the oxidized tungsten surface are discussed. It is shown, that the ESD originates by the electron transition from the interval 5p- or 5s shell of the tungsten surface atom onto the oxygen external unfilled 2p-level

Structural and electronic properties of carbon nanotubes under hydrostatic pressures

International Nuclear Information System (INIS)

Zhang Ying; Cao Juexian; Yang Wei

2008-01-01

We studied the structural and electronic properties of carbon nanotubes under hydrostatic pressures based on molecular dynamics simulations and first principles band structure calculations. It is found that carbon nanotubes experience a hard-to-soft transition as external pressure increases. The bulk modulus of soft phase is two orders of magnitude smaller than that of hard phase. The band structure calculations show that band gap of (10, 0) nanotube increases with the increase of pressure at low pressures. Above a critical pressure (5.70GPa), band gap of (10, 0) nanotube drops rapidly and becomes zero at 6.62GPa. Moreover, the calculated charge density shows that a large pressure can induce an sp 2 -to-sp 3 bonding transition, which is confirmed by recent experiments on deformed carbon nanotubes

Electronic transport properties of fullerene functionalized carbon nanotubes: Ab initio and tight-binding calculations

DEFF Research Database (Denmark)

Fürst, Joachim Alexander; Hashemi, J.; Markussen, Troels

2009-01-01

Fullerene functionalized carbon nanotubes-NanoBuds-form a novel class of hybrid carbon materials, which possesses many advantageous properties as compared to the pristine components. Here, we report a theoretical study of the electronic transport properties of these compounds. We use both ab init...

Beam Tests of Diamond-Like Carbon Coating for Mitigation of Electron Cloud

Energy Technology Data Exchange (ETDEWEB)

Eldred, Jeffrey [Fermilab; Backfish, Michael [Fermilab; Kato, Shigeki [KEK, Tsukuba; Tan, Cheng-Yang [Fermilab; Zwaska, Robert [Fermilab

2017-05-01

Electron cloud beam instabilities are an important consideration in virtually all high-energy particle accelerators and could pose a formidable challenge to forthcoming high-intensity accelerator upgrades. Our results evaluate the efficacy of a diamond-like carbon (DLC) coating for the mitigation of electron in the Fermilab Main Injector. The interior surface of the beampipe conditions in response to electron bombardment from the electron cloud and we track the change in electron cloud flux over time in the DLC coated beampipe and uncoated stainless steel beampipe. The electron flux is measured by retarding field analyzers placed in a field-free region of the Main Injector. We find the DLC coating reduces the electron cloud signal to roughly 2\\% of that measured in the uncoated stainless steel beampipe.

Transmission Electron Microscopy Study of Individual Carbon Nanotube Breakdown Caused by Joule Heating in Air

DEFF Research Database (Denmark)

Mølhave, Kristian; Gudnason, S.B.; Pedersen, Anders Tegtmeier

2006-01-01

We present repeated structural and electrical measurements on individual multiwalled carbon nanotubes, alternating between electrical measurements under ambient conditions and transmission electron microscopy (TEM). The multiwalled carbon nanotubes made by chemical vapor deposition were manipulated...

Raman spectroscopy as a tool to investigate the structure and electronic properties of carbon-atom wires

Directory of Open Access Journals (Sweden)

Alberto Milani

2015-02-01

Full Text Available Graphene, nanotubes and other carbon nanostructures have shown potential as candidates for advanced technological applications due to the different coordination of carbon atoms and to the possibility of π-conjugation. In this context, atomic-scale wires comprised of sp-hybridized carbon atoms represent ideal 1D systems to potentially downscale devices to the atomic level. Carbon-atom wires (CAWs can be arranged in two possible structures: a sequence of double bonds (cumulenes, resulting in a 1D metal, or an alternating sequence of single–triple bonds (polyynes, expected to show semiconducting properties. The electronic and optical properties of CAWs can be finely tuned by controlling the wire length (i.e., the number of carbon atoms and the type of termination (e.g., atom, molecular group or nanostructure. Although linear, sp-hybridized carbon systems are still considered elusive and unstable materials, a number of nanostructures consisting of sp-carbon wires have been produced and characterized to date. In this short review, we present the main CAW synthesis techniques and stabilization strategies and we discuss the current status of the understanding of their structural, electronic and vibrational properties with particular attention to how these properties are related to one another. We focus on the use of vibrational spectroscopy to provide information on the structural and electronic properties of the system (e.g., determination of wire length. Moreover, by employing Raman spectroscopy and surface enhanced Raman scattering in combination with the support of first principles calculations, we show that a detailed understanding of the charge transfer between CAWs and metal nanoparticles may open the possibility to tune the electronic structure from alternating to equalized bonds.

Ultrafast electron transfer in all-carbon-based SWCNT-C60 donor-acceptor nanoensembles connected by poly(phenylene-ethynylene) spacers

Science.gov (United States)

Barrejón, Myriam; Gobeze, Habtom B.; Gómez-Escalonilla, María J.; Fierro, José Luis G.; Zhang, Minfang; Yudasaka, Masako; Iijima, Sumio; D'Souza, Francis; Langa, Fernando

2016-08-01

Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an electron donating or accepting photosensitizer while the second part should fulfil the role of an electron acceptor or donor. In the present work, we have successfully addressed this issue by synthesizing covalently linked all-carbon-based donor-acceptor nanoensembles using single-walled carbon nanotubes (SWCNTs) as the donor and C60 as the acceptor. The donor-acceptor entities in the nanoensembles were connected by phenylene-ethynylene spacer units to achieve better electronic communication and to vary the distance between the components. These novel SWCNT-C60 nanoensembles have been characterized by a number of techniques, including TGA, FT-IR, Raman, AFM, absorbance and electrochemical methods. The moderate number of fullerene addends present on the side-walls of the nanotubes largely preserved the electronic structure of the nanotubes. The thermodynamic feasibility of charge separation in these nanoensembles was established using spectral and electrochemical data. Finally, occurrence of ultrafast electron transfer from the excited nanotubes in these donor-acceptor nanohybrids has been established by femtosecond transient absorption studies, signifying their utility in building light energy harvesting devices.Building all-carbon based functional materials for light energy harvesting applications could be a solution to tackle and reduce environmental carbon output. However, development of such all-carbon based donor-acceptor hybrids and demonstration of photoinduced charge separation in such nanohybrids is a challenge since in these hybrids part of the carbon material should act as an

Electron energy-loss spectroscopy characterization and microwave absorption of iron-filled carbon-nitrogen nanotubes

International Nuclear Information System (INIS)

Che Renchao; Liang Chongyun; Shi Honglong; Zhou Xingui; Yang Xinan

2007-01-01

Iron-filled carbon-nitrogen (Fe/CN x ) nanotubes and iron-filled carbon (Fe/C) nanotubes were synthesized at 900 deg. C through a pyrolysis reaction of ferrocene/acetonitrile and ferrocene/xylene, respectively. The differences of structure and composition between the Fe/CN x nanotubes and Fe/C nanotubes were investigated by transmission electron microscopy and electron energy-loss spectroscopy (EELS). It was found that the morphology of Fe/CN x nanotubes is more corrugated than that of the Fe/C nanotubes due to the incorporation of nitrogen. By comparing the Fe L 2,3 electron energy-loss spectra of Fe/CN x nanotubes to those of the Fe/C nanotubes, the electron states at the interface between Fe and the tubular wall of both Fe/CN x nanotubes and Fe/C nanotubes were investigated. At the boundary between Fe and the wall of a CN x nanotube, the additional electrons contributed from the doped 'pyridinic-like' nitrogen might transfer to the empty 3d orbital of the encapsulated iron, therefore leading to an intensity suppression of the iron L 2,3 edge and an intensity enhancement of the carbon K edge. However, such an effect could not be found in Fe/C nanotubes. Microwave absorption properties of both Fe/CN x and Fe/C nanocomposites at 2-18 GHz band were studied

Synergistic effect of single-electron-trapped oxygen vacancies and carbon species on the visible light photocatalytic activity of carbon-modified TiO2

International Nuclear Information System (INIS)

Wang, Xiaodong; Xue, Xiaoxiao; Liu, Xiaogang; Xing, Xing; Li, Qiuye; Yang, Jianjun

2015-01-01

Carbon-modified TiO 2 (CT) nanoparticles were prepared via a two-step method of heat treatment without the resorcinol-formaldehyde (RF) polymer. As-prepared CT nanoparticles were characterized by means of X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis/DRS), transmission electron microscopy (TEM), N 2 adsorption–desorption isotherms, thermal analysis (TA), electron spin resonance (ESR), and X-ray photoelectron spectroscopy (XPS). The visible light photocatalytic activities were evaluated on the basis of the degradation of methyl orange (MO). The synergistic effect of single-electron-trapped oxygen vacancies (SETOVs) and the carbon species on the visible light photocatalytic activities of the CT nanoparticles were discussed. It was found that the crystalline phase, the morphology, and particle size of the CT nanoparticles depended on the second heat-treatment temperature instead of the first heat-treatment temperature. The visible light photocatalytic activities were attributed to the synergistic effect of SETOVs and the carbon species, and also depended on the specific surface area of the photocatalysts. - Highlights: • Carbon-modified TiO 2 particles have been prepared without RF polymer. • The visible light photocatalytic activities of the particles have been evaluated. • The band gap energy structure of the carbon-modified TiO 2 has been proposed. • Synergistic effect of SETOVs and carbon species has been discussed. • The activities also depend on the specific surface area of the catalysts

Successive ionization of positive ions of carbon and nitrogen by electron bombardment

International Nuclear Information System (INIS)

Donets, E.D.; Ilyushchenko, V.I.

Experimental studies of deep ionization of heavy ions are described. The applications of such studies in atomic physics, plasma physics and space physics are discussed. Investigations using intersecting ion-electron beams, shifted beams and ion trap sources are described, and data are presented for multi-charged ions of carbon, oxygen and nitrogen. A detailed description of the development of the IEL (electron beam ionizer) source, and the KRION (cryogenic version) source is given, and further data for the multiple ionization of carbon and nitrogen are given for charge states up to C 6+ and N 7+ . The advantages and disadvantages of the KRION source are discussed, and preliminary studies of a new torroidal ion trap source (HIRAC) are presented. (11 figs, 57 refs) (U.S.)

Carbon amendment stimulates benthic nitrogen cycling during the bioremediation of particulate aquaculture waste

Science.gov (United States)

Robinson, Georgina; MacTavish, Thomas; Savage, Candida; Caldwell, Gary S.; Jones, Clifford L. W.; Probyn, Trevor; Eyre, Bradley D.; Stead, Selina M.

2018-03-01

The treatment of organic wastes remains one of the key sustainability challenges facing the growing global aquaculture industry. Bioremediation systems based on coupled bioturbation-microbial processing offer a promising route for waste management. We present, for the first time, a combined biogeochemical-molecular analysis of the short-term performance of one such system that is designed to receive nitrogen-rich particulate aquaculture wastes. Using sea cucumbers (Holothuria scabra) as a model bioturbator we provide evidence that adjusting the waste C : N from 5 : 1 to 20 : 1 promoted a shift in nitrogen cycling pathways towards the dissimilatory nitrate reduction to ammonium (DNRA), resulting in net NH4+ efflux from the sediment. The carbon amended treatment exhibited an overall net N2 uptake, whereas the control receiving only aquaculture waste exhibited net N2 production, suggesting that carbon supplementation enhanced nitrogen fixation. The higher NH4+ efflux and N2 uptake was further supported by meta-genome predictions that indicate that organic-carbon addition stimulated DNRA over denitrification. These findings indicate that carbon addition may potentially result in greater retention of nitrogen within the system; however, longer-term trials are necessary to determine whether this nitrogen retention is translated into improved sea cucumber biomass yields. Whether this truly constitutes a remediation process is open for debate as there remains the risk that any increased nitrogen retention may be temporary, with any subsequent release potentially raising the eutrophication risk. Longer and larger-scale trials are required before this approach may be validated with the complexities of the in-system nitrogen cycle being fully understood.

Negative ion emission at field electron emission from amorphous (alpha-C:H) carbon

CERN Document Server

Bernatskij, D P; Ivanov-Omskij, V I; Pavlov, V G; Zvonareva, T K

2001-01-01

The study on the electrons field emission from the plane cathode surface on the basis of the amorphous carbon film (alpha-C:H) is carried out. The methodology, making it possible to accomplish simultaneously the registration of the emission currents and visually observe the distribution of the emission centers on the plane emitter surface is developed. The analysis of the oscillograms indicated that apart from the proper electron constituent the negative ions of hydrogen (H sup - and H sub 2 sup -), carbon (C sup -) and hydrocarbon (CH sub n sup -) are observed. The ions emission is connected with the processes of formation and degradation of the local emission centers

The influence of electron discharge and magnetic field on calcium carbonate (CaCO{sub 3}) precipitation

Energy Technology Data Exchange (ETDEWEB)

Putro, Triswantoro, E-mail: tris@physics.its.ac.id; Endarko, E-mail: endarko@physics.its.ac.id [Physics Department, Faculty of Mathematics and Natural Science Institut Teknologi Sepuluh Nopember (ITS), Surabaya 60111 (Indonesia)

2016-04-19

The influences of electron discharge and magnetic field on calcium carbonate (CaCO{sub 3}) precipitation in water have been successfully investigated. The study used three pairs of magnetic field 0.1 T whilst the electron discharge was generated from television flyback transformer type BW00607 and stainless steel SUS 304 as an electrode. The water sample with an initial condition of 230 mg/L placed in the reactor with flow rate 375 mL/minutes, result showed that the electron discharge can be reduced contain of calcium carbonate the water sample around 17.39% within 2 hours. Meanwhile for the same long period of treatment and flow rate, around 56.69% from initial condition of 520 mg/L of calcium carbonate in the water sample can be achieved by three pairs of magnetic field 0.1 T. When the combination of three pairs of magnetic field 0.1 T and the electron discharge used for treatment, the result showed that the combination of electron discharge and magnetic field methods can be used to precipitate calcium carbonate in the water sample 300 mg/L around 76.66% for 2 hours of treatment. The study then investigated the influence of the polar position of the magnetic field on calcium carbonate precipitation. Two positions of magnetic field were tested namely the system with alternated polar magnetics and the system without inversion of the polar magnetics. The influence of the polar position showed that the percentage reduction in levels of calcium carbonate in the water sample (360 mg/L) is significant different. Result showed that the system without inversion of the polar magnetics is generally lower than the system with alternated polar magnetics, with reduction level at 30.55 and 57.69%, respectively.

Optically stimulated luminescence in electronic components for emergency dosimetry

International Nuclear Information System (INIS)

Geber-Bergstrand, T.; Bernhardsson, C.; Mattsson, S.; Raeaef, C.L.

2015-01-01

Document available in abstract form only. Full text of publication follows: Accidents and, luckily more rarely, attacks involving nuclear or radiological material do occur from time to time. A very possible consequence of an accident or attack of this kind is that nearby people might be exposed to ionising radiation. Since these types of exposure situations, unlike the ones occurring in medicine, are unplanned, there are no radiation-monitoring data available. For several reasons, it is nevertheless of value to find out the dose that these people have received. The first and most urgent reason is after-the-event triage, to be able to carry out proper medical treatments and also to focus the available medical assets to the persons needing it the most. This is where different retrospective dosimetry techniques, such as luminescence, can be employed. Various electronic components from mobile phones and other portable devices have been studied using optically stimulated luminescence for their potential use in retrospective dosimetry. Previous investigations have been performed in laboratory conditions and have showed very promising properties for emergency dosimetry. In this study, the more practical parts of using electronic components in retrospective dosimetry have been considered. In a triage situation, one of the key parameters to consider is time; thus, effort has been made to speed up the readout procedure, yet without the loss of too much accuracy. (authors)

Light-harvesting dendrimer zinc-phthalocyanines chromophores labeled single-wall carbon nanotube nanoensembles: Synthesis and photoinduced electron transfer

Energy Technology Data Exchange (ETDEWEB)

Yang, Hongqin [Key Laboratory of Optoelectronic Science and Technology for Medicine, Ministry of Education and Fujian Provincial Key Laboratory for Photonics Technology, Fujian Normal University, Fuzhou 350007 (China); Pan, Sujuan; Ma, Dongdong; He, Dandan; Wang, Yuhua [College of Chemistry & Engineering, Fujian Provincial Key Laboratory of Polymer Materials, Fujian Normal University, Fuzhou 350007 (China); Xie, Shusen [Key Laboratory of Optoelectronic Science and Technology for Medicine, Ministry of Education and Fujian Provincial Key Laboratory for Photonics Technology, Fujian Normal University, Fuzhou 350007 (China); Peng, Yiru, E-mail: yirupeng@fjnu.edu.cn [College of Chemistry & Engineering, Fujian Provincial Key Laboratory of Polymer Materials, Fujian Normal University, Fuzhou 350007 (China)

2016-11-15

A novel series of light-harvesting dendrimer zinc-phthalocyanines chromophores labeled-single-wall carbon nanotubes (SWNTs) nanoparticles, in which 0–2 generations dendrimer zinc phthalocyanines covalently linked with SWNTs using either ethylenediamine or hexamethylenediamine as the space linkers were prepared. The structures and morphologies of these nanoconjugates were comprehensively characterized by Raman spectroscopy, transmission electron microscopy and thermal gravimetric analysis methods. Their photophysical properties were investigated by fluorescence and time-resolved spectroscopic methods. The photoinduced intramolecular electron transfer occurred from phthalocyanines (donors) to SWNTs (acceptors). Besides, the electron transfer exchange rates and exchange efficacies between the dendritic phthalocyanines and single-wall carbon nanotubes increased as the length of spacer linker decreased, or as the dendritic generation increased. Cyclic voltammetry (CV) method further confirmed thermodynamics possibility of the electron transfer from phthalocyanines to single-wall carbon nanotubes. These new nanoconjugates are fundamentally important due to the synergy effects of both carbon nanotubes and dendrimer phthalocyanines, which may find potential applications in the fields of drug delivery, biological labeling, or others.

Measurements of Wake-Riding Electrons in Antiproton-Carbon-Foil Collisions

CERN Multimedia

2002-01-01

When a charged particle passes through dielectric media, e.g. a thin carbon foil, a ``wake'' is induced. The characteristic wake-potential shows an oscillatory behaviour, with a wavelength of about $ 2 \\pi v _{p} / \\omega _{p} _{l} $ where $ v _{p} $ is the projectile velocity and $ \\omega _{p} _{l} $ the plasmon energy of the target. This induced wake potential is superimposed on the Coulomb potential of the projectile, the latter leading to a pronounced ``cusp'' of electrons leaving the solid at $ v _{e} app v _{p} $ for positively charged projectiles in the MeV region. Correspondingly, an ``anti-cusp'' is expected for antiprotons. \\\\ \\\\ In the solid, the wake-potential leads to an attractive force on electrons, and a dynamic electronic state is predicted both for proton and antiproton projectiles. In the solid, the wake-riding electrons are travelling with the projectile speed $ v _{p} $ Upon exit of the foil, the electron released from the wake-riding state of an antiproton will suddenly find itself in th...

Electron tunneling in carbon nanotube composites

International Nuclear Information System (INIS)

Gau, C; Kuo, Cheng-Yung; Ko, H S

2009-01-01

Nanocomposites, such as polymer blending with carbon nanotubes (CNTs), have been shown to have a drastic reduction in the resistivity and become conductive when the CNTs concentration has reached a certain percolation threshold. The reduction could be more than a millionth of the original polymer material. This has been realized as the formation of an infinite cluster of connected CNTs or pathways. Therefore, the conductivity of a nanocomposite should follow that of CNTs. Here we show that the resistivity of a nanocomposite is not governed by the interconnected CNTs, but the polymer between neighboring CNTs. That is, polymer-CNTs exhibit the nature of a conducting polymer, which can be explained as the tunneling of electrons one by one from the first CNT electrode to the next-nearest CNT electrode, forming a CNT/polymer pathway. A conduction model based on the tunneling of electrons passing, one by one, through the polymer gap between two neighboring CNT electrodes is formulated and derived. This model can accurately predict the significant reduction of the polymer-CNTs' resistivity with the addition of CNTs. The temperature effect can be readily incorporated to account for resistivity variation with the temperature of this nanocomposites.

Electronic structure and transport properties of quasi-one-dimensional carbon nanomaterials

Directory of Open Access Journals (Sweden)

Y. N. Wu

2017-09-01

Full Text Available Based on the density functional theory combined with the nonequilibrium Green’s function, the influence of the wrinkle on the electronic structures and transport properties of quasi-one-dimensional carbon nanomaterials have been investigated, in which the wrinkled armchair graphene nanoribbons (wAGNRs and the composite of AGNRs and single walled carbon nanotubes (SWCNTs were considered with different connection of ripples. The wrinkle adjusts the electronic structures and transport properties of AGNRs. With the change of the strain, the wAGNRs for three width families reveal different electrical behavior. The band gap of AGNR(6 increases in the presence of the wrinkle, which is opposite to that of AGNR(5 and AGNR(7. The transport of AGNRs with the widths 6 or 7 has been modified by the wrinkle, especially by the number of isolated ripples, but it is insensitive to the strain. The nanojunctions constructed by AGNRs and SWCNTs can form the quantum wells, and some specific states are confined in wAGNRs. Although these nanojunctions exhibit the metallic, they have poor conductance due to the wrinkle. The filling of C20 into SWCNT has less influence on the electronic structure and transport of the junctions. The width and connection type of ripples have greatly influenced on the electronic structures and transport properties of quasi-one-dimensional nanomaterials.

Electronic structure and transport properties of quasi-one-dimensional carbon nanomaterials

Science.gov (United States)

Wu, Y. N.; Cheng, P.; Wu, M. J.; Zhu, H.; Xiang, Q.; Ni, J.

2017-09-01

Based on the density functional theory combined with the nonequilibrium Green's function, the influence of the wrinkle on the electronic structures and transport properties of quasi-one-dimensional carbon nanomaterials have been investigated, in which the wrinkled armchair graphene nanoribbons (wAGNRs) and the composite of AGNRs and single walled carbon nanotubes (SWCNTs) were considered with different connection of ripples. The wrinkle adjusts the electronic structures and transport properties of AGNRs. With the change of the strain, the wAGNRs for three width families reveal different electrical behavior. The band gap of AGNR(6) increases in the presence of the wrinkle, which is opposite to that of AGNR(5) and AGNR(7). The transport of AGNRs with the widths 6 or 7 has been modified by the wrinkle, especially by the number of isolated ripples, but it is insensitive to the strain. The nanojunctions constructed by AGNRs and SWCNTs can form the quantum wells, and some specific states are confined in wAGNRs. Although these nanojunctions exhibit the metallic, they have poor conductance due to the wrinkle. The filling of C20 into SWCNT has less influence on the electronic structure and transport of the junctions. The width and connection type of ripples have greatly influenced on the electronic structures and transport properties of quasi-one-dimensional nanomaterials.

Electronic properties of carbon nanotubes with polygonized cross sections

International Nuclear Information System (INIS)

Charlier, J.; Lambin, P.; Ebbesen, T.

1996-01-01

The electronic properties of carbon nanotubes having polygonized cross sections instead of purely circular ones, such as recently observed using transmission electron microscopy, are investigated with plane-wave ab initio pseudopotential local-density-functional calculations and simple tight-binding models. Strong σ * -π * hybridization effects occur in zigzag nanotubes due to the high curvature located near the edges of the polygonal cross-section prism. These effects, combined with a lowering of symmetry, dramatically affect the electronic properties of the nanotubes. It is found that modified low-lying conduction-band states are introduced either into the bandgap of insulating nanotubes, or below the degenerate states that form the top of the valence band of metallic nanotubes, leading the corresponding nanostructures to be metals, semimetals, or at least very-small-gap semiconductors. The degree of the polygon representing the cross section of the tube, and the sharpness of the edge angles, are found to be major factors in the hybridization effect, and consequently govern the electronic behavior at the Fermi level. copyright 1996 The American Physical Society

Electron stimulated desorption study of oxygen adsorption on tungsten

International Nuclear Information System (INIS)

Prince, R.H.; Floyd, G.R.

1978-01-01

The adsorption of oxygen on a polycrystalline tungsten surface at approximately 800 K has been studied by means of electron stimulated desorption (ESD). Although precision gas dosing was not employed, the initial sticking probability for dissociative adsorption appears to be essentially unity, while the variation with coverage suggests that a high degree of order exists and that precursor state kinetics are significant. A most noticeable and reproducible discontinuity in ESD parameters occurs at a fractional coverage theta approximately 0.8 (exposure approximately 1.4 X 10 15 molecules/cm 2 incident) which is interpreted as an order-disorder transition within a single (β 1 ) chemisorption state, and results in an increase in the ionic desorption cross-section by a factor of approximately 1.26. A discussion of the adsorption kinetics and the disorder transition is given in terms of current models of dissociative adsoption which include the effects of nearest neighbour lateral interactions. (Auth.)

Creation of paired electron states in the gap of semiconducting carbon nanotubes by correlated hydrogen adsorption

International Nuclear Information System (INIS)

Buchs, Gilles; Krasheninnikov, Arkady V; Ruffieux, Pascal; Groening, Pierangelo; Foster, Adam S; Nieminen, Risto M; Groening, Oliver

2007-01-01

The specific, local modification of the electronic structure of carbon nanomaterials is as important for novel electronic device fabrication as the doping in the case of silicon-based electronics. Here, we report low temperature scanning tunneling microscopy and spectroscopy study of semiconducting carbon nanotubes subjected to hydrogen-plasma treatment. We show that plasma treatment mostly results in the creation of paired electronic states in the nanotube band gap. Combined with extensive first-principle simulations, our results provide direct evidence that these states originate from correlated chemisorption of hydrogen adatoms on the tube surface. The energy splitting of the paired states is governed by the adatom-adatom interaction, so that controlled hydrogenation can be used for engineering the local electronic structure of nanotubes and other sp 2 -bonded nanocarbon systems

Gold and palladium adsorption from leached electronic scrap using ordered mesoporous carbon nanoscaffolds

Energy Technology Data Exchange (ETDEWEB)

McDowell, Rocklan; Dutech, Guy

2014-09-01

Ordered mesoporous carbon (OMC) nanoscaffolds are engineered agglomerates of carbon nanotubes held together by small carbon nanofibers with uniform pore sizes, high pore volume, and high channel permeability. These materials exhibit very high affinity for the adsorption of gold from aqueous acidic mixtures. The efficiency of gold recovery is comparable to those typically accomplished using biopolymer-based adsorbents. The adsorption efficiency for other precious metals such as palladium and platinum is lower. Studies on the precious metal (Au, Pd) adsorption on OMC materials from actual liquors of leached electronics will be presented. Adsorption properties will be compared for several different sorbents used for the recovery of precious metals. The leach liquor compositions for three different types of electronic scrap materials (personal computer board, cell phone and tv input/output board) will be presented. The sorption efficiencies for Au, Pd, together with a spectrum of competing and non-competing metals, from such leach mixtures will be compared.

Gold and palladium adsorption from leached electronic scrap using ordered mesoporous carbon nanoscaffolds

International Nuclear Information System (INIS)

McDowell, Rocklan; Dutech, Guy

2014-01-01

Ordered mesoporous carbon (OMC) nanoscaffolds are engineered agglomerates of carbon nanotubes held together by small carbon nanofibers with uniform pore sizes, high pore volume, and high channel permeability. These materials exhibit very high affinity for the adsorption of gold from aqueous acidic mixtures. The efficiency of gold recovery is comparable to those typically accomplished using biopolymer-based adsorbents. The adsorption efficiency for other precious metals such as palladium and platinum is lower. Studies on the precious metal (Au, Pd) adsorption on OMC materials from actual liquors of leached electronics will be presented. Adsorption properties will be compared for several different sorbents used for the recovery of precious metals. The leach liquor compositions for three different types of electronic scrap materials (personal computer board, cell phone and tv input/output board) will be presented. The sorption efficiencies for Au, Pd, together with a spectrum of competing and non-competing metals, from such leach mixtures will be compared.

Optically stimulated luminescence of electronic components for forensic, retrospective, and accident dosimetry

International Nuclear Information System (INIS)

Inrig, E.L.; Godfrey-Smith, D.I.; Khanna, S.

2008-01-01

This study investigated the optically stimulated luminescence (OSL) response of electronic components found within portable electronic devices such as cell phones and pagers, portable computers, music and video players, global positioning system receivers, cameras, and digital watches. The analysis of components extracted from these ubiquitous devices was proposed for applications ranging from rapid accident dose reconstruction to the tracking and attribution of gamma-emitting radiological materials. Surface-mount resistors with alumina porcelain substrates consistently produced OSL following irradiation, with minimum detectable doses on the order of 10 mGy for a typical sample. Since the resistor ceramics were found to exhibit anomalous fading, dose reconstruction procedures were developed to correct for this using laboratory measurements of fading rates carried out over approximately 3 months. Two trials were conducted in which cellular phones were affixed to an anthropomorphic phantom and irradiated using gamma-ray sources; ultimately, analysis of the devices used in these trials succeeded in reconstructing doses in the range of 0.1-0.6Gy

UV photon and low-energy (5--150 eV) electron-stimulated processes at environmental interfaces

International Nuclear Information System (INIS)

Orlando, T.M.

1997-01-01

Irradiation of surfaces and interfaces with low-energy (5--150 eV) electrons and ultraviolet photons occurs during the storage of ''mixed'' (chemical/radioactive) waste forms and during processing steps which involve the use of low temperature plasmas. It is well known that electron- and photon-stimulated desorption (ESD and PSD) from wide band-gap materials and interfaces can be initiated by Auger decay of deep valence and shallow core holes. This process consists of hole production, Auger decay, reversal of the Madelung potential, and ion expulsion due to the Coulomb repulsion. ESD and PSD of neutrals also occurs and involves production of electron-hole pairs and excitons. Generally, neutral yields dominate ESD and PSD cross sections, which typically vary between ∼10 -16 and 10 -22 cm 2 . The authors present results on the ESD and PSD of environmentally relevant substrates such as ZrO 2 (100), soda-glass, and NaNO 3 . The major cation thresholds and yields indicate that ESD and PSD from these complex materials involves Auger stimulated events. In particular, desorption thresholds correlate with ionization of the O(2s), Zr(4p), Si(2p) and Na(2s) levels. The near band-gap threshold energy (∼5--7 eV) for the desorption of neutrals (i.e., atomic oxygen, NO, etc) demonstrate the overall importance of self-trapped and localized excitons in both ESD and PSD of typical ceramics and oxides

Performance Enhancement of Organic Light-Emitting Diodes Using Electron-Injection Materials of Metal Carbonates

Science.gov (United States)

Shin, Jong-Yeol; Kim, Tae Wan; Kim, Gwi-Yeol; Lee, Su-Min; Shrestha, Bhanu; Hong, Jin-Woong

2016-05-01

Performance of organic light-emitting diodes was investigated depending on the electron-injection materials of metal carbonates (Li2CO3 and Cs2CO3 ); and number of layers. In order to improve the device efficiency, two types of devices were manufactured by using the hole-injection material (Teflon-amorphous fluoropolymer -AF) and electron-injection materials; one is a two-layer reference device ( ITO/Teflon-AF/Alq3/Al ) and the other is a three-layer device (ITO/Teflon-AF/Alq3/metal carbonate/Al). From the results of the efficiency for the devices with hole-injection layer and electron-injection layer, it was found that the electron-injection layer affects the electrical properties of the device more than the hole-injection layer. The external-quantum efficiency for the three-layer device with Li2CO3 and Cs2CO3 layer is improved by approximately six and eight times, respectively, compared with that of the two-layer reference device. It is thought that a use of electron-injection layer increases recombination rate of charge carriers by the active injection of electrons and the blocking of holes.

Performance of Carbon Coatings for Mitigation of Electron Cloud in the SPS

CERN Document Server

Yin Vallgren, C; Costa Pinto, P; Neupert, H; Rumolo, G; Shaposhnikova, E; Taborelli, M; Kato, S

2011-01-01

Amorphous carbon (a-C) coatings have been tested in electron cloud monitors (ECM) in the Super Proton Synchrotron (SPS) and have shown for LHC type beams a reduction of the electron cloud current by a factor 104 compared to stainless steel (StSt). This performance has been maintained for more than 3 years under SPS operation conditions. Secondary electron yield (SEY) laboratory data confirm that after more than 1 year of SPS operation, the coating maintains a SEY below 1.0. The compatibility of coexisting StSt and a-C surfaces has been studied in an ECM having coated and uncoated areas. The results show no degradation of the properties of the a-C areas. The performance of diamond like carbon (DLC) coating has also been studied. DLC shows a less effective reduction of the EC current than a-C, but conditioning is faster than for StSt. Three a-C coated dipoles were inserted in the SPS. However, even with no EC detected, the dynamic pressure rise is similar to the one observed in the StSt reference dipoles. Measu...

Backscattered electron emission after proton impact on carbon and gold films: Experiments and simulations

Energy Technology Data Exchange (ETDEWEB)

Hespeels, F.; Heuskin, A.C. [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium); Scifoni, E. [TIFPA-INFN, Trento Institute for Fundamental Physics and Applications, Via Sommarive 14, I-38123 Trento (Italy); GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Kraemer, M. [GSI-Helmholtzzentrum für Schwerionenforschung, Biophysik, Max Planck-Strasse 1, D-64291 Darmstadt (Germany); Lucas, S., E-mail: stephane.lucas@unamur.be [University of Namur, PMR, 61 rue de Bruxelles, B-5000 Namur (Belgium)

2017-06-15

This work aims at measuring the proton induced secondary electron energy spectra from nanometer thin films. Backscattered electron energy spectra were measured within an energy range from 0 to 600 eV using a Retarding Field Analyser (RFA). This paper presents energy spectra obtained for proton (0.5 MeV; 1 MeV; 1.5 MeV; 2 MeV) irradiation of thin carbon films (50 and 100 nm thick) and thin gold film (200 nm). These experimental spectra were compared with Monte Carlo simulations based on TRAX code and Geant4 simulation toolkit. Good agreement between experimental, TRAX and Geant4 results were observed for the carbon target. For the gold target, we report major differences between both Monte Carlo environments. Limitation of Geant4 models for low energy electron emission was highlighted. On the contrary, TRAX simulations present encouraging results for the modeling of low-energy electron emission from gold target.

Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments

NARCIS (Netherlands)

Rubio-Bollinger, G.; Castellanos-Gomez, A.; Bilan, S.; Zotti, L.A.; Arroyo, C.R.; Agraït, N.; Cuevas, J.

2012-01-01

We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron

Modification of anisotropic plasma diffusion via auxiliary electrons emitted by a carbon nanotubes-based electron gun in an electron cyclotron resonance ion source.

Science.gov (United States)

Malferrari, L; Odorici, F; Veronese, G P; Rizzoli, R; Mascali, D; Celona, L; Gammino, S; Castro, G; Miracoli, R; Serafino, T

2012-02-01

The diffusion mechanism in magnetized plasmas is a largely debated issue. A short circuit model was proposed by Simon, assuming fluxes of lost particles along the axial (electrons) and radial (ions) directions which can be compensated, to preserve the quasi-neutrality, by currents flowing throughout the conducting plasma chamber walls. We hereby propose a new method to modify Simon's currents via electrons injected by a carbon nanotubes-based electron gun. We found this improves the source performances, increasing the output current for several charge states. The method is especially sensitive to the pumping frequency. Output currents for given charge states, at different auxiliary electron currents, will be reported in the paper and the influence of the frequency tuning on the compensation mechanism will be discussed.

Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

Energy Technology Data Exchange (ETDEWEB)

Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, D-85747 Garching (Germany); Rao, B. Jayachander [Departamento de Química and Centro de Química, Universidade de Coimbra, 3004-535 Coimbra (Portugal)

2016-05-14

We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

Thermally stimulated exoelectron emission from solid Xe

International Nuclear Information System (INIS)

Khyzhniy, I.V.; Grigorashchenko, O.N.; Savchenko, E.V.; Ponomarev, A.N.; Bondybey, V.E.

2007-01-01

Thermally-stimulated emission of exoelectrons and photons from solid Xe pre-irradiated by low-energy electrons were studied. A high sensitivity of thermally-stimulated luminescence (TSL) and thermally-stimulated exoelectron emission (TSEE) to sample prehistory was demonstrated. It was shown that electron traps in unannealed samples are characterized by much broader distribution of trap levels in comparison with annealed samples and their concentration exceeds in number that in annealed samples. Both phenomena, TSL and TSEE, were found to be triggered by release of electrons from the same kind of traps. The data obtained suggest a competition between two relaxation channels: charge recombination and electron transport terminated by TSL and TSEE. It was found that TSEE predominates at low temperatures while at higher temperatures TSL prevails. An additional relaxation channel, a photon-stimulated exoelectron emission pre-irradiated solid Xe, was revealed

Half-metallicity and electronic structures for carbon-doped group III-nitrides: Calculated with a modified Becke-Johnson potential

Science.gov (United States)

Fan, Shuai-wei; Wang, Ri-gao; Xu, Pemg

2016-09-01

The electronic structures and magnetism for carbon-doped group III-nitrides are investigated by utilizing the first principle method with the modified Becke-Johnson potential. Calculations show that carbon substituting cations (anions) would induce the group III-nitrides to be paramagnetic metals (half-metallic ferromagnets). Single carbon substituting nitrogen could produce 1.00μB magnetic moment. Electronic structures indicate that the carriers-mediated double-exchange interaction plays a crucial role in forming the ferromagnetism. Based on the mean-field theory, the Curie temperature for carbon-doped group III-nitrides would be above the room temperature. Negative chemical pair interactions imply that carbon dopants tend to form clustering distribution in group III-nitrides. The nitrogen vacancy would make the carbon-doped group III-nitrides lose the half-metallic ferromagnetism.

Ohmic contact junction of carbon nanotubes fabricated by in situ electron beam deposition

International Nuclear Information System (INIS)

Wang, Y G; Wang, T H; Lin, X W; Dravid, V P

2006-01-01

We present experimental evidence of in situ fabrication of multi-walled carbon nanotube junctions via electron beam induced deposition. The tip-to-tip interconnection of the nanotubes involves the alignment of two nanotubes via a piezodriven nanomanipulator and nano-welding by electron beam deposition. Hydrocarbon contamination from the pump oil vapour of the vacuum system of the TEM chamber was used as the solder; this is superior to the already available metallic solders because its composition is identical to the carbon nanotube. The hydrocarbon deposition, with perfect wettability, on the nanotubes establishes strong mechanical binding between the two nanotubes to form an integrated structure. Consequently, the nanotubes cross-linked by the hydrocarbon solder produce good electrical and mechanical connections. The joint dimension was determined by the size of the electron beam, which results in a sound junction with well-defined geometry and the smallest junction size obtained so far. In situ electric measurement showed a linear current-voltage property for the multi-walled nanotube junction

Curling and closure of graphitic networks under electron-beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Ugarte, D [Ecole Polytechnique Federale, Lausanne (Switzerland)

1992-10-22

The discovery of buckminsterfullerene (C[sub 60]) and its production in macroscopic quantities has stimulated a great deal of research. More recently, attention has turned towards other curved graphitic networks, such as the giant fullerenes (C[sub n], n > 100) and carbon nanotubes. A general mechanism has been proposed in which the graphitic sheets bend in an attempt to eliminate the highly energetic dangling bonds present at the edge of the growing structure. Here, I report the response of carbon soot particles and tubular graphitic structures to intense electron-beam irradiation in a high-resolution electron microscope; such conditions resemble a high-temperature regime, permitting a degree of structural fluidity. With increased irradiation, there is a gradual reorganization of the initial material into quasi-spherical particles composed of concentric graphitic shells. This lends weight to the nucleation scheme proposed for fullerenes, and moreover, suggests that planar graphite may not be the most stable allotrope of carbon in systems of limited size. (Author).

Large flexibility of high aspect ratio carbon nanostructures fabricated by electron-beam-induced deposition

Energy Technology Data Exchange (ETDEWEB)

Beard, J D; Gordeev, S N, E-mail: jdb28@bath.ac.uk [Department of Physics, University of Bath, Bath BA2 7AY (United Kingdom)

2010-11-26

The mechanical properties of free-standing electron beam deposited amorphous carbon structures have been studied using atomic force microscopy. The fabricated carbon blades are found to be extraordinarily flexible, capable of undergoing vertical deflection up to {approx} 75% of their total length without inelastic deformation. The elastic bending modulus of these structures was calculated to be 28 {+-} 10 GPa.

The Range of 1-3 keV Electrons in Solid Oxygen and Carbon Monoxide

DEFF Research Database (Denmark)

Oehlenschlæger, M.; Andersen, H.H.; Schou, Jørgen

1985-01-01

The range of 1-3 keV electrons in films of solid oxygen and carbon monoxide has been measured by a mirror substrate method. The technique used here is identical to the one previously used for range measurements in solid hydrogen and nitrogen. The range in oxygen is slightly shorter than that in n......The range of 1-3 keV electrons in films of solid oxygen and carbon monoxide has been measured by a mirror substrate method. The technique used here is identical to the one previously used for range measurements in solid hydrogen and nitrogen. The range in oxygen is slightly shorter than...

A high resolution electron microscopy investigation of curvature in carbon nanotubes

Science.gov (United States)

Weldon, D. N.; Blau, W. J.; Zandbergen, H. W.

1995-07-01

Evidence for heptagon inclusion in multi-walled carbon nanotubes was sought in arc-produced carbon deposits. Transmission electron microscopy revealed many curved nanotubes although their relative abundance was low. Close examination of the micrographs in the regions of expected heptagon inclusion shows that the curvature is accomplished by folding or fracture of the lattice planes. This observed phenomenon contradicts the theoretical modelling studies which predict stable structures with negative curvature accomplished by heptagon/pentagon pairs. A possible explanation for curvature in single-walled tubes is presented based on a molecular mechanics geometry optimisation study of spa inclusion in a graphite sheet.

Carbonate radical anion-induced electron transfer in bovine serum albumin

Energy Technology Data Exchange (ETDEWEB)

Joshi, Ravi [Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085 (India)]. E-mail: rjudrin@yahoo.com; Mukherjee, T. [Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2006-07-15

Reaction of native and thermally denatured bovine serum albumin (BSA) with carbonate radical anion (CO{sub 3}{sup -} radical) has been studied using pulse radiolysis technique. Scavenging of CO{sub 3}{sup -} radical by native BSA and consequent electron transfer from tyrosine to tryptophan radical has been observed to occur with almost same rate constant (k{approx}1.7x10{sup 8} dm{sup 3} mol{sup -1} s{sup -1}) at pH 8.8. Effect of structural changes, due to thermal denaturation, on scavenging of CO{sub 3}{sup -} radical and the electron transfer process have been studied and discussed in this paper.

Carbon nanotube transistor based high-frequency electronics

Science.gov (United States)

Schroter, Michael

At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

Synthesis of carbon nanorods by reduction of carbon bisulfide

International Nuclear Information System (INIS)

Lou Zhengsong; He Minglong; Zhao Dejian; Li Zhongchun; Shang Tongming

2010-01-01

Research highlights: Our manuscript is a concise preliminary account of original and of significant research, which illuminates carbon nanorods and variously shaped Y-junction carbon nanorods are successfully fabricated on a large scale through a carbon bisulfide thermal reduction process. Various shaped Y-junction carbon nanorods can be used as studying the electronic and transport properties of the nano-meter carbon material. - Abstract: Carbon nanorods are synthesized at large scale by the reduction of carbon bisulfide at 600 o C. Moreover, novel Y-junction carbon nanorods are detected in the samples. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and N 2 physisorption studies show that carbon nanorods predominate in the product. Based on the supercritical carbon bisulfide system, the possible growth mechanism of the carbon nanorods was discussed. This method provides a simple and cheap route to large-scale synthesis of carbon nanorods.

Analysis of hydrogen distribution on Mg-Ni alloy surface by scanning electron-stimulated desorption ion microscope (SESDIM)

International Nuclear Information System (INIS)

Yamaga, Atsushi; Hibino, Kiyohide; Suzuki, Masanori; Yamada, Masaaki; Tanaka, Kazuhide; Ueda, Kazuyuki

2008-01-01

Hydrogen distribution and behavior on a Mg-Ni alloy surface are studied by using a time-of-flight electron-stimulated desorption (TOF-ESD) microscopy and a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). The desorbed hydrogen ions are energy-discriminated and distinguished into two characters in the adsorbed states, which belong to Mg 2 Ni grains and the other to oxygen-contaminated Mg phase at the grain boundaries. Adsorbed hydrogen is found to be stable up to 150 deg. C, but becomes thermally unstable around at 200 deg. C

Electronic Structure of Single- and Multiple-shell Carbon Fullerenes

OpenAIRE

Lin, Yeong-Lieh; Nori, Franco

1993-01-01

We study the electronic states of giant single-shell and the recently discovered nested multi-shell carbon fullerenes within the tight-binding approximation. We use two different approaches, one based on iterations and the other on symmetry, to obtain the $\\pi$-state energy spectra of large fullerene cages: $C_{240}$, $C_{540}$, $C_{960}$, $C_{1500}$, $C_{2160}$ and $C_{2940}$. Our iteration technique reduces the dimensionality of the problem by more than one order of magnitude (factors of $\\...

Electron field emission characteristics of carbon nanotube on tungsten tip

International Nuclear Information System (INIS)

Phan Ngoc Hong; Bui Hung Thang; Nguyen Tuan Hong; Phan Ngoc Minh; Lee, Soonil

2009-01-01

Electron field emission characteristic of carbon nanotubes on tungsten tip was investigated in 2x10 -6 Torr vacuum. The measurement results showed that the CNTs/W tip could emit electron at 0.7 V/μm (nearly 10 times lower than that of the W tip itself) and reach up to 26 μA at the electric field of 1 V/μm. The emission characteristic follows the Fowler-Nordheim mechanism. Analysis of the emission characteristic showed that the CNTs/W tip has a very high value of field enhancement factor (β = 4.1 x 10 4 cm -1 ) that is much higher than that of the tungsten tip itself. The results confirmed the excellent field emission behavior of the CNTs materials and the CNTs/W tip is a prospective candidate for advanced electron field emitter.

Transformation of carbon tetrachloride in an anaerobic packed-bed reactor without addition of another electron donor

NARCIS (Netherlands)

de Best, JH; Hunneman, P; Doddema, HJ; Janssen, DB; Harder, W; Doddema, Hans J.

1999-01-01

Carbon tetrachloride (52 mu M) was biodegraded for more than 72% in an anaerobic packed-bed reactor without addition of an external electron donor. The chloride mass balance demonstrated that all carbon tetrachloride transformed was completely dechlorinated. Chloroform and dichloromethane were

Transformation of carbon tetrachloride in an anaerobic packed-bed reactor without addition of another electron donor

NARCIS (Netherlands)

Best, J.H. de; Hunneman, P.; Doddema, H.J.; Janssen, D.B.; Harder, W.

1999-01-01

Carbon tetrachloride (52 μM) was biodegraded for more than 72% in an anaerobic packed-bed reactor without addition of an external electron donor. The chloride mass balance demonstrated that all carbon tetrachloride transformed was completely dechlorinated. Chloroform and dichloromethane were

Ab initio study on the electronic transport properties of carbon nanotube intramolecular junctions

Energy Technology Data Exchange (ETDEWEB)

Wang, R.N. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Graduate School of the Chinese Academy of Sciences, 19A Yu Quan Rd, Beijing 100049 (China); Zheng, X.H.; Zeng, Z. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Song, L.L. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Graduate School of the Chinese Academy of Sciences, 19A Yu Quan Rd, Beijing 100049 (China); School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009 (China)

2011-12-15

The effects of electron doping and molecule adsorption on the electronic transport properties of carbon nanotube (CNT) junctions CNT(3,3)/n-CNT(6,0)/CNT(3,3) (n = 1-5) are simulated by first-principles calculations combined with a non-equilibrium Green's function technique. The doping effects are investigated by N substitution for the carbon atom while the molecule adsorption effects are studied by adsorbing a H{sub 2}O molecule or an OH group on the top of one carbon atom, respectively. The transmission function around the Fermi level is highly dependent on the doping or adsorption site. The effects are negligible when the site is at the interface, while it always forms a scattering barrier which causes a valley of the transmission spectra around the Fermi level when the doping/adsorption site is inside the sandwiched CNT(6,0). The conductance of CNT intramolecular junctions is very sensitive to the environment, which may provide potential of application in future nanoelectronic devices and gas sensors. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

High frequency conductivity of hot electrons in carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Amekpewu, M., E-mail: mamek219@gmail.com [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, S.Y. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Musah, R. [Department of Applied Physics, University for Development Studies, Navrongo (Ghana); Mensah, N.G. [Department of Mathematics, College of Agriculture and Natural Sciences, U.C.C. (Ghana); Abukari, S.S.; Dompreh, K.A. [Department of Physics, College of Agriculture and Natural Sciences, U.C.C. (Ghana)

2016-05-01

High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac–dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons’ source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

Electronic transport properties of carbon nanotube metal-semiconductor-metal

Directory of Open Access Journals (Sweden)

F Khoeini

2008-07-01

Full Text Available  In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT attached to semi-infinite clean metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states(LDOS in the metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices.

Electron percolation in realistic models of carbon nanotube networks

International Nuclear Information System (INIS)

Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain

2015-01-01

The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models

Carbon nanotube foils for electron stripping in tandem accelerators

International Nuclear Information System (INIS)

Reden, Karl von; Zhang Mei; Meigs, Martha; Sichel, Enid; Fang Shaoli; Baughman, Ray H.

2007-01-01

Carbon nanotube technology has rapidly advanced in recent years, making it possible to create meter-long, ∼4 cm wide films of multi-walled tubes of less than 3 μg/cm 2 areal density in a bench top open-air procedure. The physical properties of individual carbon nanotubes have been well established, equaling or surpassing electrical and thermal conductivity and mechanical strength of most other materials, graphite in particular. The handling and transport of such nanotube films, dry-mounted self-supporting on metal frames with several cm 2 of open area, is problem-free: the aerogel films having a volumetric density of about 1.5 mg/cm 3 survived the trip by car and air from Dallas to Oak Ridge without blemish. In this paper we will present the results of first tests of these nanotube films as electron stripper media in a tandem accelerator. The tests were performed in the Model 25 URC tandem accelerator of the Holifield radioactive ion beam facility (HRIBF) at Oak Ridge National Laboratory. We will discuss the performance of nanotube films in comparison with chemical vapor deposition and laser-ablated carbon foils

Electron percolation in realistic models of carbon nanotube networks

Science.gov (United States)

Simoneau, Louis-Philippe; Villeneuve, Jérémie; Rochefort, Alain

2015-09-01

The influence of penetrable and curved carbon nanotubes (CNT) on the charge percolation in three-dimensional disordered CNT networks have been studied with Monte-Carlo simulations. By considering carbon nanotubes as solid objects but where the overlap between their electron cloud can be controlled, we observed that the structural characteristics of networks containing lower aspect ratio CNT are highly sensitive to the degree of penetration between crossed nanotubes. Following our efficient strategy to displace CNT to different positions to create more realistic statistical models, we conclude that the connectivity between objects increases with the hard-core/soft-shell radii ratio. In contrast, the presence of curved CNT in the random networks leads to an increasing percolation threshold and to a decreasing electrical conductivity at saturation. The waviness of CNT decreases the effective distance between the nanotube extremities, hence reducing their connectivity and degrading their electrical properties. We present the results of our simulation in terms of thickness of the CNT network from which simple structural parameters such as the volume fraction or the carbon nanotube density can be accurately evaluated with our more realistic models.

A study of point defects created by electron irradiation of dilute iron-carbon alloys

International Nuclear Information System (INIS)

Leveque, J.L.

1969-10-01

Resistivity and magnetic after effect (m.a.e.) measurements are used to study the influence of carbon atoms on the annealing process of point defects created by electron irradiation (3 MeV) at low temperature (20 deg. K). The presence of the carbon atoms has a strong influence on the recovery sub-stage I E and stage III. For the former, the carbon impurity traps the freely migrating iron interstitial. For the latter the effect is interpreted as being due to formation during annealing, of a carbon vacancy pair. A pronounced m.a.e. band is attributed to the reorientation of this carbon vacancy complex. All these results are coherent with the interpretation of a low temperature migrating free interstitial. (author) [fr

Diamond surface: atomic and electronic structure

International Nuclear Information System (INIS)

Pate, B.B.

1984-01-01

Experimental studies of the diamond surface (with primary emphasis on the (111) surface) are presented. Aspects of the diamond surface which are addressed include (1) the electronic structure, (2) the atomic structure, and (3) the effect of termination of the lattice by foreign atoms. Limited studies of graphite are discussed for comparison with the diamond results. Experimental results from valence band and core level photoemission spectroscopy (PES), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and carbon 1s near edge x-ray absorption fine structure (NEXAFS) spectroscopy (both the total electron yield (TEY) and Auger electron yield (AEY) techniques) are used to study and characterize both the clean and hydrogenated surface. In addition, the interaction of hydrogen with the diamond surface is examined using results from vibrational high resolution low energy electron loss spectroscopy (in collaboration with Waclawski, Pierce, Swanson, and Celotta at the National Bureau of Standards) and photon stimulated ion desorption (PSID) yield at photon energies near the carbon k-edge (hv greater than or equal to 280 eV). Both EELS and PSID verify that the mechanically polished 1 x 1 surface is hydrogen terminated and also that the reconstructed surface is hydrogen free. The (111) 2 x 2/2 x 1 reconstructed surface is obtained from the hydrogenated (111) 1 x 1:H surface by annealing to approx. = 1000 0 C. We observe occupied intrinsic surface states and a surface chemical shift (0.95 +- 0.1 eV) to lower binding energy of the carbon 1s level on the hydrogen-free reconstructed surface. Atomic hydrogen is found to be reactive with the reconstructed surface, while molecular hydrogen is relatively inert. Exposure of the reconstructed surface to atomic hydrogen results in chemisorption of hydrogen and removal of the intrinsic surface state emission in and near the band gap region

Multiwalled carbon nanotube destruction in the radiation damages to electron irradiation

Directory of Open Access Journals (Sweden)

T. M. Pinchuk-Rugal’

2015-10-01

Full Text Available Behavior of the X-ray diffraction and vibrational Raman spectra of multiwalled carbon nanotubes (MWCNT under high-energy electron irradiation (Ee = 1.8 MeV with large doses of absorption to 10 MGy were studied. With increasing dose uptake to 10.0 MGy, the interlayer correlation in the distribution of the individual graphene nanotubes nets not only is maintained, but is even improved. Defective bands D, D' and G band with increasing dose absorption have significant transformation, which show radiation damages of MWCNT. The destruction of nanotubes under electron irradiation is accompanied by increased regulation in the arrangement of individual nanotubes by interlayer cross-links involving interstitial atoms. The severity of degradation and cross-linking of MWCNT depends on the electron absorption dose.

Hierarchical meso/macro-porous carbon fabricated from dual MgO templates for direct electron transfer enzymatic electrodes

Science.gov (United States)

Funabashi, Hiroto; Takeuchi, Satoshi; Tsujimura, Seiya

2017-03-01

We designed a three-dimensional (3D) hierarchical pore structure to improve the current production efficiency and stability of direct electron transfer-type biocathodes. The 3D hierarchical electrode structure was fabricated using a MgO-templated porous carbon framework produced from two MgO templates with sizes of 40 and 150 nm. The results revealed that the optimal pore composition for a bilirubin oxidase-catalysed oxygen reduction cathode was a mixture of 33% macropores and 67% mesopores (MgOC33). The macropores improve mass transfer inside the carbon material, and the mesopores improve the electron transfer efficiency of the enzyme by surrounding the enzyme with carbon.

High-resolution transmission electron microscopy and energetics of flattened carbon nonoshells

International Nuclear Information System (INIS)

Bourgeois, L.N.; Bursill, L.A.

1998-01-01

When examined under a high-resolution transmission electron microscope, carbon soot produced alongside buckytubes in an arc-discharge is found to contain a small percentage of flattened carbon shells. These objects are shown to be small graphite flakes which eliminated their dangling bonds by terminating their edges with highly curved junctions. Ideal models for these structures are presented, and their energy estimated. The calculations show that the establishment of highly curved junctions is energetically favourable for a graphite flake in an inert atmosphere. Flattened shells also appear more stable than their 'inflated' counterparts (fullerene 'onions' and buckytubes) when the shell dimensions obey specific criteria.(authors)

Enabling fast electron transfer through both bacterial outer-membrane redox centers and endogenous electron mediators by polyaniline hybridized large-mesoporous carbon anode for high-performance microbial fuel cells

International Nuclear Information System (INIS)

Zou, Long; Qiao, Yan; Zhong, Canyu; Li, Chang Ming

2017-01-01

Both physical structure and chemical property of an electrode play critical roles in extracellular electron transfer from microbes to electrodes in microbial fuel cells (MFCs). Herein a novel polyaniline hybridized large mesoporous carbon (PANI-LMC) anode is fabricated from natural biomass by nanostructured CaCO 3 template-assisted carbonization followed by in situ chemical polymerizing PANI to enable fast extracellular electron transfer, in which the LMC with rich disorder-interconnected large mesopores (∼20−50 nm) and large surface area facilitates a fast mediated electron transfer through electron mediators, while the decorated PANI on LMC surface enables the direct electron transfer via bacterial outer-membrane redox centers. Owing to the unique synergistic effect from both excellent electron transfer paths, the PANI-LMC hybrid anode harvests high power electricity with a maximum output power density of 1280 mW m −2 in Shewanella putrefaciens CN32 MFCs, 10-fold higher than that of conventional carbon cloth. The findings from this work suggest a new insight on design of high-efficient anode according to the multiple and flexible electrochemical process for practical MFC applications.

Short-term effects of carbon dioxide on carnation callus cell respiration

International Nuclear Information System (INIS)

Palet, A.; Ribas-Carbo, M.; Argiles, J.M.; Azcon-Bieto, J.

1991-01-01

The addition of potassium bicarbonate to the electrode cuvette immediately stimulated the rate of dark O 2 uptake of photomixotrophic and heterotrophic carnation (Dianthus caryophyllus L.) callus, of Elodea canadensis (Minchx) leaves, and of other plant tissues. This phenomenon occurred at pH values lower than 7.2 to 7.8, and the stimulation depended on the concentration of gaseous CO 2 in the solution. These stimulatory responses lasted several minutes and then decreased, but additional bicarbonate or gaseous CO 2 again stimulated respiration, suggesting a reversible effect. Carbonic anhydrase in the solution increased the stimulatory effect of potassium bicarbonate. The CO 2 /bicarbonate dependent stimulation of respiration did not occur in animal tissues such as rat diaphragm and isolated hepatocytes, and was inhibited by salicylhydroxamic acid in carnation callus cells and E. canadensis leaves. This suggested that the alternative oxidase was engaged during the stimulation in plant tissues. The cytochrome pathway was severely inhibited by CO 2 /bicarbonate either in the absence or in the presence of the uncoupler carbonylcyanide m-chlorophenyl hydrazone. The activity of cytochrome c oxidase of callus tissue homogenates was also inhibited by CO 2 /bicarbonate. The results suggested that high carbon dioxide levels (mainly free CO 2 ) partially inhibited the cytochrome pathway (apparently at the oxidase level), and this block in electron transport elicited a large transient engagement of the alternative oxidase when present uninhibited

Enhancement of ECR performances by means of carbon nano-tubes based electron guns

International Nuclear Information System (INIS)

Odorici, F.; Cuffiani, M.; Malferrari, L.; Rizzoli, R.; Veronese, G.P.; Celona, L.; Gammino, S.; Mascali, D.; Miracoli, R.; Romano, F.P.; Gambino, N.; Castro, G.; Ciavola, G.; Serafino, T.

2012-01-01

The CANTES experiment at INFN-LNS tested the use of carbon nano-tubes (CNTs) to emit electrons by field emission effect, in order to provide additional electrons to the plasma core of an ECR ion source. This technique was used with the Caesar source, demonstrating that the total extracted ion current is increased and that a relevant reduction of the number of 'high energy' electrons (above 100 keV) may be observed. The injection of additional electrons inside the plasma increases the amount of cold and warm electrons, and then the number of ionizing collisions. Details of the construction of CNTs based electron gun and of the improvement of performances of the Caesar ECR ion source will be presented. The paper is followed by the associated poster. (authors)

High resolution transmission electron microscopic study of nanoporous carbon consisting of curved single graphite sheets

International Nuclear Information System (INIS)

Bourgeois, L.N.; Bursill, L.A.

1997-01-01

A high resolution transmission electron microscopic study of a nanoporous carbon rich in curved graphite monolayers is presented. Observations of very thin regions. including the effect of tilting the specimen with respect to the electron beam, are reported. The initiation of single sheet material on an oriented graphite substrate is also observed. When combined with image simulations and independent measurements of the density (1.37g cm -3 ) and sp 3 /sp 2 +sp 2 bonding fraction (0.16), these observations suggest that this material is a two phase mixture containing a relatively low density aggregation of essentially capped single shells like squat nanotubes and polyhedra, plus a relatively dense 'amorphous' carbon structure which may be described using a random-Schwarzite model. Some negatively-curved sheets were also identified in the low density phase. Finally, some discussion is offered regarding the growth mechanisms responsible for this nanoporous carbon and its relationship with the structures of amorphous carbons across a broad range of densities, porosities and sp 3 /sp 2 +sp 3 bonding fractions

Molecular effects in carbon K-shell Auger-electron production by 0.6-2.0 MeV protons and extraction of an atomic cross section

International Nuclear Information System (INIS)

McDaniel, F.D.; Lapicki, G.

1987-01-01

Carbon K-shell Auger-electron production cross sections are reported for 0.6-2.0 MeV protons incident on CH 4 (methane), C 2 H 2 (acetylene), C 2 H 4 (ethylene), C 2 H 6 (ethane), n-C 4 H 10 (normal butane), i-C 4 H 10 (isobutane), C 6 H 6 (benzene), CO (carbon monoxide), and CO 2 (carbon dioxide). A constant-energy mode 45 0 parallel-plate electrostatic analyzer was used for detection of Auger electrons. The carbon KLL Auger-electron cross sections for all molecules were found to be lower than that found for CH 4 by 9-23%. All carbon KLL Auger-electron data could be brought into agreement when corrected for the chemical shift of the carbon K-shell binding energy in molecules and for intramolecular scattering. KLL Auger-electron production cross sections are compared to first Born and ECPSSR theories and show good agreement with both after the chemical shift of the carbon K-shell binding energy in molecules and the effects of intramolecular scattering are considered. (orig.)

Effect of interwall interaction on the electronic structure of double-walled carbon nanotubes

International Nuclear Information System (INIS)

Soto, M; Boyer, T A; Biradar, S; Ge, L; Vajtai, R; Ajayan, P M; Barrera, E V; Elías-Zúñiga, A

2015-01-01

Through this study, the results of density functional theory calculations within the local density approximation of the electronic structure of zigzag–zigzag double-walled carbon nanotubes (DWCNTs), with chiral indices (n, 0)@(m, 0) for n = 7–15, and m = 15–26, has been presented and the effects of interwall interaction and orbital hybridization on the electronic structure of these systems has been discussed. It was observed that the electronic band gap of the aforementioned DWCNTs depends on the interwall distance only for metallic–semiconductor configurations and on the intrinsic properties of the constituent tubes in all other combinations. It was also observed that the calculated band gap for most of the metallic–metallic DWCNTs was smaller than semiconductor–metallic, metallic–semiconductor, and semiconductor–semiconductor configurations. Metallic–semiconductor DWCNTs were found to be desirable for band gap tuning applications because of their dependence on interwall distance, opening up the possibility of using such systems in electronic device applications, such as transistors. Other applications include the use of DWCNTs in macroscopic carbon nanotube conducting wires, for which metallic–metallic and semiconducting–metallic zigzag–zigzag DWCNTs were found to be the most desirable configurations due to their small band gaps. (paper)

Electron emission from nano-structured carbon composite materials and fabrication of high-quality electron emitters by using plasma technology

International Nuclear Information System (INIS)

Hiraki, H.; Hiraki, A.; Jiang, N.; Wang, H. X.

2006-01-01

Many trials have been done to fabricate high-quality electron-emitters from nano-composite carbon materials (such as nano-diamond, carbon nano tubes and others) by means of a variety of plasma chemical-vapor-deposition (CVD) techniques. Based upon the mechanism of electron emission, we have proposed several strategic guide lines for the fabrication of good emitters. Then, following these lines, several types of emitters were tried. One of the emitters has shown a worldclass, top ranking for fabricating very bright lamps: namely, a low turn-on voltage (0.5 ∼ 1 V/μm to induce 10 μA/cm 2 emission current) to emit a 1 mA/cm 2 current at 3 V/μm and 100 mA/cm 2 current at a slightly higher applied voltage. The bright lamps are Mercury-free fluorescence lamps to exhibit brightness of ∼10 5 cd/m 2 with high efficiency of ∼100 lm/w.

Three-dimensional machining of carbon nanotube forests using water-assisted scanning electron microscope processing

Energy Technology Data Exchange (ETDEWEB)

Rajabifar, Bahram; Maschmann, Matthew R., E-mail: MaschmannM@missouri.edu [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Kim, Sanha; Hart, A. John [Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Slinker, Keith [Materials and Manufacturing Directorate, AFRL/RX, Air Force Research Lab, Ohio 45433 (United States); Universal Technology Corporation, Beavercreek, Ohio 45424 (United States); Ehlert, Gregory J. [Materials and Manufacturing Directorate, AFRL/RX, Air Force Research Lab, Ohio 45433 (United States)

2015-10-05

We demonstrate that vertically aligned carbon nanotubes (CNTs) can be precisely machined in a low pressure water vapor ambient using the electron beam of an environmental scanning electron microscope. The electron beam locally damages the irradiated regions of the CNT forest and also dissociates the water vapor molecules into reactive species including hydroxyl radicals. These species then locally oxidize the damaged region of the CNTs. The technique offers material removal capabilities ranging from selected CNTs to hundreds of cubic microns. We study how the material removal rate is influenced by the acceleration voltage, beam current, dwell time, operating pressure, and CNT orientation. Milled cuts with depths between 0–100 microns are generated, corresponding to a material removal rate of up to 20.1 μm{sup 3}/min. The technique produces little carbon residue and does not disturb the native morphology of the CNT network. Finally, we demonstrate direct machining of pyramidal surfaces and re-entrant cuts to create freestanding geometries.

Three-dimensional machining of carbon nanotube forests using water-assisted scanning electron microscope processing

Science.gov (United States)

Rajabifar, Bahram; Kim, Sanha; Slinker, Keith; Ehlert, Gregory J.; Hart, A. John; Maschmann, Matthew R.

2015-10-01

We demonstrate that vertically aligned carbon nanotubes (CNTs) can be precisely machined in a low pressure water vapor ambient using the electron beam of an environmental scanning electron microscope. The electron beam locally damages the irradiated regions of the CNT forest and also dissociates the water vapor molecules into reactive species including hydroxyl radicals. These species then locally oxidize the damaged region of the CNTs. The technique offers material removal capabilities ranging from selected CNTs to hundreds of cubic microns. We study how the material removal rate is influenced by the acceleration voltage, beam current, dwell time, operating pressure, and CNT orientation. Milled cuts with depths between 0-100 microns are generated, corresponding to a material removal rate of up to 20.1 μm3/min. The technique produces little carbon residue and does not disturb the native morphology of the CNT network. Finally, we demonstrate direct machining of pyramidal surfaces and re-entrant cuts to create freestanding geometries.

Intensity dependent waiting time for strong electron trapping events in speckle stimulated raman scatter

Energy Technology Data Exchange (ETDEWEB)

Rose, Harvey [Los Alamos National Laboratory; Daughton, W [Los Alamos National Laboratory; Yin, L [Los Alamos National Laboratory

2009-01-01

The onset of Stimulated Raman scatter from an intense laser speckle is the simplest experimentally realizable laser-plasma-interaction environment. Despite this data and recent 3D particle simulations, the controlling mechanism at the onset of backscatter in the kinetic regime when strong electron trapping in the daughter Langmuir wave is a dominant nonlinearity is not understood. This paper explores the consequences of assuming that onset is controlled by large thermal fluctuations. A super exponential dependence of mean reflectivity on speckle intensity in the onset regime is predicted.

Electron transfer mediators accelerated the microbiologically influence corrosion against carbon steel by nitrate reducing Pseudomonas aeruginosa biofilm.

Science.gov (United States)

Jia, Ru; Yang, Dongqing; Xu, Dake; Gu, Tingyue

2017-12-01

Electron transfer is a rate-limiting step in microbiologically influenced corrosion (MIC) caused by microbes that utilize extracellular electrons. Cross-cell wall electron transfer is necessary to transport the electrons released from extracellular iron oxidation into the cytoplasm of cells. Electron transfer mediators were found to accelerate the MIC caused by sulfate reducing bacteria. However, there is no publication in the literature showing the effect of electron transfer mediators on MIC caused by nitrate reducing bacteria (NRB). This work demonstrated that the corrosion of anaerobic Pseudomonas aeruginosa (PAO1) grown as a nitrate reducing bacterium biofilm on C1018 carbon steel was enhanced by two electron transfer mediators, riboflavin and flavin adenine dinucleotide (FAD) separately during a 7-day incubation period. The addition of either 10ppm (w/w) (26.6μM) riboflavin or 10ppm (12.7μM) FAD did not increase planktonic cell counts, but they increased the maximum pit depth on carbon steel coupons considerably from 17.5μm to 24.4μm and 25.0μm, respectively. Riboflavin and FAD also increased the specific weight loss of carbon steel from 2.06mg/cm 2 to 2.34mg/cm 2 and 2.61mg/cm 2 , respectively. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization curves all corroborated the pitting and weight loss data. Copyright © 2017 Elsevier B.V. All rights reserved.

Electric field effect in the growth of carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Plaza, E., E-mail: ericvpp@gmail.com; Briceño-Fuenmayor, H. [Instituto Venezolano de Investigaciones Científicas (IVIC), Laboratorio de Física de Fluidos y Plasma (Venezuela, Bolivarian Republic of); Arévalo, J. [Instituto Zuliano de Investigaciones Tecnológicas (INZIT), Unidad de Caracterización y Estructura de Materiales (Venezuela, Bolivarian Republic of); Atencio, R. [Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Investigación y Tecnología de Materiales (Venezuela, Bolivarian Republic of); Corredor, L. [Instituto Zuliano de Investigaciones Tecnológicas (INZIT), Unidad de Caracterización y Estructura de Materiales (Venezuela, Bolivarian Republic of)

2015-06-15

The growth of carbon nanotubes (CNTs) under a controlled electric field in a chemical vapor deposition system is investigated. We evaluate the influence of this external field on the morphological and structural characteristics of CNTs. Scanning electron microscopy results display a large presence of carbonaceous material in the positive plate, which appear to be a consequence of the attraction of electric forces over the electronically unbalanced cracked carbon molecules in the heating zone. We also observe a growth behavior for CNTs, in which catalyst particles are localized either at the bottom or the upper part of the nanotube, depending on the intensity and direction of the electric field. A Raman analysis from all obtained carbon materials shows the presence of two peaks, corresponding to the D ∼ 1340 cm{sup −1} and G ∼ 1590 cm{sup −1} bands attributed to multiwall CNTs. The average diameter of the CNTs is in the range between 90 and 40 nm. These results provide experimental evidence for the dependence of the catalyst and subtract interaction on the growing mechanism, in which weak chemical or electronic interactions could stimulate a top-growing as the strongest base-growing process.

Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

Science.gov (United States)

Srivastava, Deepak; Saini, Subhash (Technical Monitor)

1998-01-01

The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

Implementation of Carbon Thin Film Coatings in the Super Proton Synchrotron (SPS) for Electron Cloud Mitigation

CERN Document Server

Costa Pinto, P; Basso, T; Edwards, P; Mensi, M; Sublet, A; Taborelli, M

2014-01-01

Low Secondary Electron Yield (SEY) carbon thin films eradicate electron multipacting in accelerator beam pipes. Two magnetic cells of the SPS were coated with such material and installed. In total more than forty vacuum vessels and magnet interconnections were treated. The feasibility of the coating process was validated. The performance of the carbon thin film will be tested with LHC nominal beams after the end of the long shutdown 1. Particular attention will be drawn to the long term behaviour. This paper presents the sputtering techniques used to coat the different components; their characterization (SEY measurements on coupons, RF multipacting tests and pump down curves); and the technology to etch the carbon film in case of a faulty coating. The strategy to coat the entire SPS will also be described.

Nanotubes on Display: How Carbon Nanotubes Can Be Integrated into Electronic Displays

KAUST Repository

Opatkiewicz, Justin

2010-06-22

Random networks of single-walled carbon nanotubes show promise for use in the field of flexible electronics. Nanotube networks have been difficult to utilize because of the mixture of electronic types synthesized when grown. A variety of separation techniques have been developed, but few can readily be scaled up. Despite this issue, when metallic percolation pathways can be separated out or etched away, these networks serve as high-quality thinfilm transistors with impressive device characteristics. A new article in this issue illustrates this point and the promise of these materials. With more work, these devices can be implemented in transparent displays in the next generation of hand-held electronics. © 2010 American Chemical Society.

Music acupuncture stimulation method.

Science.gov (United States)

Brătilă, F; Moldovan, C

2007-01-01

Harmonic Medicine is the model using the theory that the body rhythms synchronize to an outer rhythm applied for therapeutic purpose, can restores the energy balance in acupuncture channels and organs and the condition of well-being. The purpose of this scientific work was to demonstrate the role played by harmonic sounds in the stimulation of the Lung (LU) Meridian (Shoutaiyin Feijing) and of the Kidney (KI) Meridian (Zushaoyin Shenjing). It was used an original method that included: measurement and electronic sound stimulation of the Meridian Entry Point, measurement of Meridian Exit Point, computer data processing, bio feed-back adjustment of the music stimulation parameters. After data processing, it was found that the sound stimulation of the Lung Meridian Frequency is optimal between 122 Hz and 128 Hz, with an average of 124 Hz (87% of the subjects) and for Kidney Meridian from 118 Hz to 121 Hz, with an average of 120 Hz (67% of the subjects). The acupuncture stimulation was more intense for female subjects (> 7%) than for the male ones. We preliminarily consider that an informational resonance phenomenon can be developed between the acupuncture music stimulation frequency and the cellular dipole frequency, being a really "resonant frequency signature" of an acupoint. The harmonic generation and the electronic excitation or low-excitation status of an acupuncture point may be considered as a resonance mechanism. By this kind of acupunctural stimulation, a symphony may act and play a healer role.

Evaporation of carbon using electrons of a high density plasma

International Nuclear Information System (INIS)

Muhl, S.; Camps, E.; Escobar A, L.; Garcia E, J.L.; Olea, O.

1999-01-01

The high density plasmas are used frequently in the preparation of thin films or surface modification, for example to nitridation. In these processes, are used mainly the ions and the neutrals which compose the plasma. However, the electrons present in the plasma are not used, except in the case of chemical reactions induced by collisions, although the electron bombardment usually get hot the work piece. Through the adequate polarization of a conductor material, it is possible to extract electrons from a high density plasma at low pressure, that could be gotten the evaporation of this material. As result of the interaction between the plasma and the electron flux with the vapor produced, this last will be ionized. In this work, it is reported the use of this novelty arrangement to prepare carbon thin films using a high density argon plasma and a high purity graphite bar as material to evaporate. It has been used substrates outside plasma and immersed in the plasma. Also it has been reported the plasma characteristics (temperature and electron density, energy and ions flux), parameters of the deposit process (deposit rate and ion/neutral rate) as well as the properties of the films obtained (IR absorption spectra and UV/Vis, elemental analysis, hardness and refractive index. (Author)

Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB2 superconductor nanomaterials

International Nuclear Information System (INIS)

Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan; Acar, Selcuk; Kokal, Ilkin; Häßler, Wolfgang

2015-01-01

Undoped and carbon-doped magnesium diboride (MgB 2 ) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB 2 samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp 3 -hybridized carbon radicals were detected. A strong reduction in the critical temperature T c was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra

A new method for detection of the electron temperature in laser-plasma short wave cut off of stimulated Raman scattering spectrum

International Nuclear Information System (INIS)

Zhang Jiatai

1994-01-01

From the theory of stimulated Raman scattering (SRS) three wave interaction, a new method of detecting the electron temperature in laser-plasma is obtained. SRS spectrum obtained from Shenguang No. 12 Nd-laser experiments are analysed. Using the wave length of short wave cut off of SRS, the electron temperature in corona plasma region is calculated consistently. These results agree reasonable with X-ray spectrum experiments

Structural, electronic properties, and quantum capacitance of B, N and P-doped armchair carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Mousavi-Khoshdel, S. Morteza, E-mail: mmousavi@iust.ac.ir [Department of Chemistry, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jahanbakhsh-bonab, Parisa [Department of Chemistry, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Targholi, Ehsan [Young Researchers and Elite Club, Abhar Branch, Islamic Azad University, Abhar (Iran, Islamic Republic of)

2016-10-07

Using DFT calculations, we study the structural parameters, electronic properties and quantum capacitance of N, B, and P-doped armchair carbon nanotubes (CNTs). Fermi level shifts towards conduction band and valence band in N- and B-doped CNTs, respectively. While in the case of P atom, despite having an extra valence electron than carbon, there is no shift in Fermi level. The results revealed from a symmetric capacitance enhancement in P-doped CNT and an asymmetric capacitance enhancement in B and N-doped CNTs. The greatest amount of quantum capacitance of N-doped (6, 6) CNT could be achieved at the concentration range of 0.1–0.15. - Highlights: • Exploration of variation in quantum capacitance of CNTs through doping N, B and P atoms. • Quantum capacitance of CNTs is sensitive to impurities entered in carbon nanotubes. • Maximum quantum capacitance of N-doped CNTs is achieved at the concentration range of 0.1–0.15.

The influence of carbon non-stoichiometry on the electronic properties of thorium monocarbide ThC

Energy Technology Data Exchange (ETDEWEB)

Shein, I.R.; Ivanovskii, A.L. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation)

2010-09-15

The first-principle band structure calculations are employed to examine the influence of carbon non-stoichiometry on the structural and electronic properties of the cubic thorium monocarbide ThC. As a result, the equilibrium geometries, electronic bands, densities of states (DOS), Sommerfeld constants and Pauli paramagnetic susceptibility for ThC{sub 1-x} (where x = 0, 0.25 and 0.50) are obtained and analyzed in comparison with available experimental data. Additionally, the formation energies of carbon vacancies are theoretically estimated for ThC{sub 1-x}. The results obtained indicate that the introduction of carbon vacancies in ThC is accompanied by pronounced DOS changes due to the appearance of novel 'vacancy states' in the near-Fermi region formed by comparable contributions of Th 6d and 5f states. The carbon deficiency strongly affects the structure and stability of thorium carbide. For example, for the hypothetical 'over-deficient' composition ThC{sub 0.50} the initial cubic structure undergoes significant tetragonal distortions. On the contrary, for ThC{sub 0.75} the value of Evf is positive and the cubic structure of this phase is preserved. (authors)

The influence of carbon non-stoichiometry on the electronic properties of thorium monocarbide ThC

International Nuclear Information System (INIS)

Shein, I.R.; Ivanovskii, A.L.

2010-01-01

The first-principle band structure calculations are employed to examine the influence of carbon non-stoichiometry on the structural and electronic properties of the cubic thorium monocarbide ThC. As a result, the equilibrium geometries, electronic bands, densities of states (DOS), Sommerfeld constants and Pauli paramagnetic susceptibility for ThC 1-x (where x = 0, 0.25 and 0.50) are obtained and analyzed in comparison with available experimental data. Additionally, the formation energies of carbon vacancies are theoretically estimated for ThC 1-x . The results obtained indicate that the introduction of carbon vacancies in ThC is accompanied by pronounced DOS changes due to the appearance of novel 'vacancy states' in the near-Fermi region formed by comparable contributions of Th 6d and 5f states. The carbon deficiency strongly affects the structure and stability of thorium carbide. For example, for the hypothetical 'over-deficient' composition ThC 0.50 the initial cubic structure undergoes significant tetragonal distortions. On the contrary, for ThC 0.75 the value of Evf is positive and the cubic structure of this phase is preserved. (authors)

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

Energy Technology Data Exchange (ETDEWEB)

Suriani, A.B., E-mail: absuriani@yahoo.com [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Dalila, A.R. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Soga, T.; Tanemura, M. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2015-10-15

Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe{sub 3}C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe{sub 3}C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm{sup −1} at current density of 1 and 10 μA cm{sup −2}, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

International Nuclear Information System (INIS)

Suriani, A.B.; Dalila, A.R.; Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N.; Soga, T.; Tanemura, M.

2015-01-01

Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe 3 C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe 3 C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm −1 at current density of 1 and 10 μA cm −2 , respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters

Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

Energy Technology Data Exchange (ETDEWEB)

Shih, Yi-Ting [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Li, Kuan-Wei [Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Honda, Shin-ichi [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Lin, Pao-Hung; Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China)

2017-06-01

Graphical abstract: The pattern design provides a new structure of surface-conduction electron-emitter display (SED). Delta-star shaped vertically aligned CNT (VACNT) arrays with 20o tips can simultaneously provide three emitters to bombard the sides of equilateral triangles pattern of VACNT, which produces numerous secondary electrons and enhance the SED efficiency. - Highlights: • The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. • The vertically aligned CNT (VACNT) arrays with 20° tips of the delta-star arrangement are used as cathodes that easily emit electrons. The cathode pattern simultaneously provides three emitters to bombard the sides of equilateral triangles pattern of VACNT. • The VACNT arrays were covered with magnesium oxide (MgO) nanostructures to promote the surface-conduction electron-emitter display (SED) efficiency (η). • The η was stably maintained in the 75–85% range. The proposed design provides a facile new method for developing SED applications. - Abstract: The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75–85% range. The proposed design provides a facile new method for

Effect of additional carbon source on naphthalene biodegradation by Pseudomonas putida G7

International Nuclear Information System (INIS)

Lee, Kangtaek; Park, Jin-Won; Ahn, Ik-Sung

2003-01-01

Addition of a carbon source as a nutrient into soil is believed to enhance in situ bioremediation by stimulating the growth of microorganisms that are indigenous to the subsurface and are capable of degrading contaminants. However, it may inhibit the biodegradation of organic contaminants and result in diauxic growth. The objective of this work is to study the effect of pyruvate as another carbon source on the biodegradation of polynuclear aromatic hydrocarbons (PAHs). In this study, naphthalene was used as a model PAH, ammonium sulfate as a nitrogen source, and oxygen as an electron acceptor. Pseudomonas putida G7 was used as a model naphthalene-degrading microorganism. From a chemostat culture, the growth kinetics of P. putida G7 on pyruvate was determined. At concentrations of naphthalene and pyruvate giving similar growth rates of P. putida G7, diauxic growth of P. putida G7 was not observed. It is suggested that pyruvate does not inhibit naphthalene biodegradation and can be used as an additional carbon source to stimulate the growth of P. putida G7 that can degrade polynuclear aromatic hydrocarbons

Electron beam irradiation effects on carbon fiber reinforced PEEK composite

International Nuclear Information System (INIS)

Sasuga, Tsuneo; Hagiwara, Miyuki; Odajima, Tosikazu; Sakai, Hideo; Nakakura, Toshiyuki; Masutani, Masahiro.

1987-03-01

Carbon fiber(CF) reinforced composites, using polyarylether-sulfone (PES) or polyarylether-ether-ketone (PEEK) as matrix material, were prepared and their electron beam irradiation effects were studied on the basis of changes in mechanical and dynamic viscoelastic properties and observation of fracture surfaces. The flexural strength of PES-CF composite decreased to 70 % of the initial strength after the irradiation of 3 MGy and 40 % after 15 MGy. The change in the profile of stress-strain (S-S) curves and fractographic observation by electron microscopy indicated that this composite irradiated with over 3 MGy was fractured by delamination caused by to the degradation of matrix polymer. The mechanical properties of PEEK-CF composite were scarcely decreased even after irradiated up to 180 MGy and this composite showed very high radiation resistance. The change in the profile of S-S curves and fractographic observation showed that this composite fractured due to destruction of fiber in the dose range less than 180 MGy, indicating that PEEK was excellent matrix material used in high radiation field. PEEK-PES-CF composite which was composed of the carbon fibers coated with PES solution showed less radiation resistance compared with PEEK-CF composite; the flexural strength decreased to 85 % of the initial value after the irradiation with 90 MGy. It was revealed from the changes in the profile of S-S curve that the specimen irradiated over 120 MGy was fractured due to not only fiber destruction but delamination. Deterioration mechanism of PEEK-PES-CF composite was studied by dynamic viscoelastic measurements in connection with the damage on matrix-fiber interface. It was suggested that the deterioration in mechanical properties of this composite was caused by the degradation of PES that coated on the surface of the carbon fibers. (author)

Analytical approach to phonons and electron-phonon interactions in single-walled zigzag carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

Kandemir, B S; Keskin, M [Department of Physics, Faculty of Sciences, Ankara University, 06100 Tandogan, Ankara (Turkey)

2008-08-13

In this paper, exact analytical expressions for the entire phonon spectra in single-walled carbon nanotubes with zigzag geometry are presented by using a new approach, originally developed by Kandemir and Altanhan. This approach is based on the concept of construction of a classical lattice Hamiltonian of single-walled carbon nanotubes, wherein the nearest and next nearest neighbor and bond bending interactions are all included, then its quantization and finally diagonalization of the resulting second quantized Hamiltonian. Furthermore, within this context, explicit analytical expressions for the relevant electron-phonon interaction coefficients are also investigated for single-walled carbon nanotubes having this geometry, by the phonon modulation of the hopping interaction.

Analytical approach to phonons and electron-phonon interactions in single-walled zigzag carbon nanotubes

International Nuclear Information System (INIS)

Kandemir, B S; Keskin, M

2008-01-01

In this paper, exact analytical expressions for the entire phonon spectra in single-walled carbon nanotubes with zigzag geometry are presented by using a new approach, originally developed by Kandemir and Altanhan. This approach is based on the concept of construction of a classical lattice Hamiltonian of single-walled carbon nanotubes, wherein the nearest and next nearest neighbor and bond bending interactions are all included, then its quantization and finally diagonalization of the resulting second quantized Hamiltonian. Furthermore, within this context, explicit analytical expressions for the relevant electron-phonon interaction coefficients are also investigated for single-walled carbon nanotubes having this geometry, by the phonon modulation of the hopping interaction

Electronic and magneto-transport in chirality sorted carbon nanotube films

Science.gov (United States)

Janas, Dawid; Czechowski, Nikodem; Adamus, Zbigniew; GiŻewski, Tomasz

2018-01-01

This research details electronic and magneto-transport in unsorted and chirality-enriched carbon nanotube (CNT) films. By measuring the electrical conductivity from 4 K to 297 K, we were able to assign the governing mechanism of electronic transport. Fluctuation-induced tunnelling was in accordance with the obtained data and very well matched the underlying physics. We demonstrated how a change in the type of CNT to make the film affects its electrical performance. As the temperature was decreased down to cryogenic conditions, up to a 56-fold increase in resistance was noted. Moreover, the measurement of magnetoresistance (MR) revealed a non-monotonic dependence on the applied magnetic field. The initial negative component of MR was eventually overpowered by the positive MR component as the field strength was increased beyond a certain threshold.

One electron oxidation of Ni(II)-iminodiacetate by carbonate radical

International Nuclear Information System (INIS)

Mandal, P.C.; Bardhan, D.K.; Bhattacharyya, S.N.

1995-01-01

Reactions of carbonate radical (CO 3 - ), generated by photolysis or by radiolysis of a carbonate solution with nickel(II)-iminodiacetate (Ni(II)IDA) were studied at pH 10.5 and ionic strength (I)=0.2 mol x dm -3 . The stable product arising from the ligand degradation in the complex is mainly glyoxalic acid. Time-resolved spectroscopy and transient kinetics were studied using flash photolysis. From the kinetic data it was suggested that the carbonate radical initially reacts with Ni(III)IDA with a rate constant (2.4.±0.4) x 10 6 dm 3 x mol -1 x s -1 to form a Ni(II)IDA species which, however, undergoes a first-order transformation (k=2.7 x 10 2 x s -1 ) to give a radical intermediate of the type Ni(II)RNHCHCO - 2 ) which rapidly forms an adduct containing a Ni-C bond. This adduct decays very slowly to give rise to glyoxalic acid. From a consideration of equilibrium between Ni(II)IDA and Ni(III)IDA, the one electron reduction potential for the Ni(III)IDA/Ni(II)IDA couple was determined to be 1.467 V. (author) 30 refs.; 5 figs

Differential multi-electron emission induced by swift highly charged gold ions penetrating carbon foils

Science.gov (United States)

Rothard, H.; Moshammer, R.; Ullrich, J.; Kollmus, H.; Mann, R.; Hagmann, S.; Zouros, T. J. M.

2007-05-01

First results on swift heavy ion induced electron emission from solids obtained with a reaction microscope are presented. This advanced technique, which is successfully used since quite some time to study electron ejection in ion-atom collisions, combines the measurement of the time-of-flight of electrons with imaging techniques. A combination of electric and magnetic fields guides the ejected electrons onto a position sensitive detector, which is capable to accept multiple hits. From position and time-of-flight measurement the full differential emission characteristics of up to 10 electrons per single incoming ion can be extracted. As a first example, we show energy spectra, angular distributions and the multiplicity distribution of electrons from impact of Au24+ (11 MeV/u) on a thin carbon foil (28 μg/cm2).

Differential multi-electron emission induced by swift highly charged gold ions penetrating carbon foils

International Nuclear Information System (INIS)

Rothard, H.; Moshammer, R.; Ullrich, J.; Kollmus, H.; Mann, R.; Hagmann, S.; Zouros, T.J.M.

2007-01-01

First results on swift heavy ion induced electron emission from solids obtained with a reaction microscope are presented. This advanced technique, which is successfully used since quite some time to study electron ejection in ion-atom collisions, combines the measurement of the time-of-flight of electrons with imaging techniques. A combination of electric and magnetic fields guides the ejected electrons onto a position sensitive detector, which is capable to accept multiple hits. From position and time-of-flight measurement the full differential emission characteristics of up to 10 electrons per single incoming ion can be extracted. As a first example, we show energy spectra, angular distributions and the multiplicity distribution of electrons from impact of Au 24+ (11 MeV/u) on a thin carbon foil (28 μg/cm 2 )

On the image formation in x-ray radiography using aligned carbon nanofibers

International Nuclear Information System (INIS)

Okuyama, F.

2017-01-01

Evidence is presented that field electrons emitted from vertically-aligned carbon nanofibers (CNFs) yield clearer x-ray images than do thermionic electrons, under the identical electron-optical condition. Specifically, the same sample, an LSI circuit, mounted on the same x-ray chamber could be imaged far more sharply with a CNF emitter than with a thermionic one. It is hypothesized that electrons discharged from CNF tips hit the target to form “discrete focal points” thereon, thereby generating multiple x-ray beams that interplay to form a brilliant, sharply-delineated x-ray image. This hypothesis may stimulate open discussion on how to define the “focal point” for the x-ray imaging using nano-structured electron sources. Also, the improved resolution attained with CNFs might indicate that the heat generation originating in electron-target interactions is not so serious in the present field-emission mode. - Highlights: • Field-emission (FE) x-ray radiography (XR) is based on nanotechnology. • FE-XR surpasses thermionic XR in image resolution and brilliance. • Highly-resolved FE-XR images are due possibly to a discrete array of x-ray spots. • This hypothesis stimulates open discussion on how to define the focal-point in FE-XR.

On the image formation in x-ray radiography using aligned carbon nanofibers

Energy Technology Data Exchange (ETDEWEB)

Okuyama, F., E-mail: okuya@mui.biglobe.ne.jp

2017-04-11

Evidence is presented that field electrons emitted from vertically-aligned carbon nanofibers (CNFs) yield clearer x-ray images than do thermionic electrons, under the identical electron-optical condition. Specifically, the same sample, an LSI circuit, mounted on the same x-ray chamber could be imaged far more sharply with a CNF emitter than with a thermionic one. It is hypothesized that electrons discharged from CNF tips hit the target to form “discrete focal points” thereon, thereby generating multiple x-ray beams that interplay to form a brilliant, sharply-delineated x-ray image. This hypothesis may stimulate open discussion on how to define the “focal point” for the x-ray imaging using nano-structured electron sources. Also, the improved resolution attained with CNFs might indicate that the heat generation originating in electron-target interactions is not so serious in the present field-emission mode. - Highlights: • Field-emission (FE) x-ray radiography (XR) is based on nanotechnology. • FE-XR surpasses thermionic XR in image resolution and brilliance. • Highly-resolved FE-XR images are due possibly to a discrete array of x-ray spots. • This hypothesis stimulates open discussion on how to define the focal-point in FE-XR.

A novel viscoelastic surfactant suitable for use in high temperature carbonate reservoirs for diverted acidizing stimulation treatments

Energy Technology Data Exchange (ETDEWEB)

Holt, Stuart; Zhou, Jian; Gadberry, Fred [AkzoNobel Surface Chemistry, Forth Worth, TX (United States); Nasr-El-Din, Hisham; Wang, Guanqun [Texas A and M University, College Station, TX (United States). Dept. of Petroleum Engineering

2012-07-01

Due to the low permeability of many carbonate hydrocarbon-bearing reservoirs, it is difficult to achieve economic hydrocarbon recovery from a well without secondary stimulation. Bullheading of strong acids, such as HCl is practiced in low temperature reservoirs, but as the bottom hole temperature (BHT) rises, the acid becomes increasingly corrosive, causing facial dissolution and sub-optimal wormhole network development. In the last decade, viscoelastic surfactants (VES) have been added to HCl acid systems to improve the stimulation of HT carbonate reservoirs. The VES form 'living polymers' or worm-like micelles as electrolyte concentration rises in the acid due to reaction with the reservoir. This leads to viscosification of the stimulation fluid. The viscosification slows further acid reaction in the region already contacted by the acid, and forces the acid to take an alternate path into the rock, leading to diversion of the acids further down the well to the harder to access toe or lower permeability zones. Until recently, the maximum BHT that such VES-based diverting systems could be used was up to about 250 deg F/120 deg C. Above that temperature, all viscous properties of the fluid are lost, destroying the mechanism of acid diversion. A recently developed novel viscoelastic surfactant provides nearly 100 deg F/55 deg C extension in the BHT range in which diverted acid treatments can be used. These fluids are able to maintain both viscosity up to about 375 deg F/190 deg C, with the elastic modulus predominating up to 350 deg F/175 deg C. It is the elasticity which is particularly important in acid diversion. These fluids can have their viscosity readily broken by in-situ hydrocarbons, dilution with water or by using a mutual solvent. The broken fluids are readily removed from the near-well bore, leaving the newly created wormhole network to produce the target hydrocarbons. The new VES is significantly more environmentally benign compared with current

A novel route to graphite-like carbon supporting SnO{sub 2} with high electron transfer and photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Chen, Xianjie; Liu, Fenglin; Liu, Bing [Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Hubei University, Wuhan 430062 (China); Ministry of Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan 430062 (China); Tian, Lihong, E-mail: tian7978@hubu.edu.cn [Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Hubei University, Wuhan 430062 (China); Ministry of Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan 430062 (China); Hu, Wei; Xia, Qinghua [Hubei Collaborative Innovation Center for Advanced Organochemical Materials, Hubei University, Wuhan 430062 (China); Ministry of Education Key Laboratory for the Synthesis and Applications of Organic Functional Molecules, Hubei University, Wuhan 430062 (China)

2015-04-28

Highlights: • Mesoporous nanocomposites that graphite-like carbon supporting SnO{sub 2} are prepared by solvothermal method combined with a post- calcination. • The polyvinylpyrrolidone not only promotes the nucleation and crystallization but also provides the carbon source in the process. • The graphite-like carbon hinders the recombination of photogenerated electron and holes efficiently. • The mesoporous carbon–SnO{sub 2} nanocomposite shows high photocatalytic activity on the degradation of Rhodamine B and glyphosate under simulated sunlight. - Abstract: Mesoporous graphite-like carbon supporting SnO{sub 2} (carbon–SnO{sub 2}) nanocomposites were prepared by a modified solvothermal method combined with a post-calcination at 500 °C under a nitrogen atmosphere. The polyvinylpyrrolidone not only promotes the nucleation and crystallization, but also provides the carbon source in the process. The results of scanning electron microscopy and transmission electron microscopy show a uniform distribution of SnO{sub 2} nanoparticles on the graphite- like carbon surface. Raman and X-ray photoelectron spectra indicate the presence of strong C–Sn interaction between SnO{sub 2} and graphite-like carbon. Photoelectrochemical measurements confirm that the effective separation of electron–hole pairs on the carbon–SnO{sub 2} nanocomposite leads to a high photocatalytic activity on the degradation of Rhodamine B and glyphosate under simulated sunlight irradiation. The nanocomposite materials show a potential application in dealing with the environmental and industrial contaminants under sunlight irradiation.

Environmental transmission electron microscopy investigations of Pt-Fe2O3 nanoparticles for nucleating carbon nanotubes

DEFF Research Database (Denmark)

He, Maoshuai; Jin, Hua; Zhang, Lili

2016-01-01

electron microscopy, restructuring of the acorn-like Pt-Fe2O3 nanoparticles at reaction conditions is investigated. Upon heating to reaction temperature, ε-Fe2O3 is converted to β-Fe2O3, which can be subsequently reduced to metallic Fe once introducing CO. As Pt promotes the carburization of Fe, part...... of the metallic Fe reacts with active carbon atoms to form Fe2.5C instead of Fe3C, catalyzing the nucleation of carbon nanotubes. Nanobeam electron diffraction characterizations on SWCNTs grown under ambient pressure at 800 °C demonstrate that their chiral angle and diameter distributions are similar to those...

Computational Nanotechnology of Molecular Materials, Electronics, and Actuators with Carbon Nanotubes and Fullerenes

Science.gov (United States)

Srivastava, Deepak; Menon, Madhu; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)

2001-01-01

The role of computational nanotechnology in developing next generation of multifunctional materials, molecular scale electronic and computing devices, sensors, actuators, and machines is described through a brief review of enabling computational techniques and few recent examples derived from computer simulations of carbon nanotube based molecular nanotechnology.

Monte Carlo simulation of electron depth distribution and backscattering for carbon films deposited on aluminium as a function of incidence angle and primary energy

Science.gov (United States)

Dapor, Maurizio

2005-01-01

Carbon films are deposited on various substrates (polymers, polyester fabrics, polyester yarns, metal alloys) both for experimental and technological motivations (medical devices, biocompatible coatings, food package and so on). Computational studies of the penetration of electron beams in supported thin film of carbon are very useful in order to compare the simulated results with analytical techniques data (obtained by scanning electron microscopy and/or Auger electron spectroscopy) and investigate the film characteristics. In the present paper, the few keV electron depth distribution and backscattering coefficient for the special case of film of carbon deposited on aluminium are investigated, by a Monte Carlo simulation, as a function of the incidence angle and primary electron energy. The simulated results can be used as a way to evaluate the carbon film thickness by a set of measurements of the backscattering coefficient.

Velocity distribution of laser photoionized neutrals ejected from methanol-dosed aluminium(111) by electron-stimulated desorption

International Nuclear Information System (INIS)

Young, C.E.; Whitten, J.E.; Pellin, M.J.; Gruen, D.M.; Jones, P.L.; Ohio State Univ., Columbus, OH

1989-01-01

Nonresonant multiphoton ionization at 193 nm wavelength was employed for efficient detection of electron-stimulated neutral desorption from Al(111) dosed with methanol to produce monolayer methoxide coverage. Velocity spectra were measured by the flight time from the crystal surface to the focal region of the laser beam with a pulsed primary electron beam of 3 keV and the sample at 300 K. Either the C + or HCO + photofragment indicated the same non-Boltzmann velocity spectrum for the neutral parent precursor with a peak kinetic energy of ∼0.1 eV. Identical distributions were obtained when the cleaned crystal was pre-oxidized with O 2 prior to methanol dosing. As the crystal temperature was raised, photoion signal from the HCO + fragment declined steadily, while C + increased until ∼550 K. The total cross section for loss of parent signal with dose of 3 keV electrons was measured to be 2±1 x 10 -17 cm -2 . 19 refs., 4 figs

Atomic layer deposition of dielectrics for carbon-based electronics

Energy Technology Data Exchange (ETDEWEB)

Kim, J., E-mail: jiyoung.kim@utdallas.edu; Jandhyala, S.

2013-11-01

Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics.

Atomic layer deposition of dielectrics for carbon-based electronics

International Nuclear Information System (INIS)

Kim, J.; Jandhyala, S.

2013-01-01

Carbon based nanomaterials like nanotubes and graphene have emerged as future generation electronic materials for device applications because of their interesting properties such as high-mobility and ability to carry high-current densities compared to conventional semiconductor materials like silicon. Therefore, there is a need to develop techniques to integrate robust gate dielectrics with high-quality interfaces for these materials in order to attain maximum performance. To date, a variety of methods including physical vapor deposition, atomic layer deposition (ALD), physical assembly among others have been employed in order to integrate dielectrics for carbon nanotube and graphene based field-effect transistors. Owing to the difficulty in wetting pristine surfaces of nanotubes and graphene, most of the ALD methods require a seeding technique involving non-covalent functionalization of their surfaces in order to nucleate dielectric growth while maintaining their intrinsic properties. A comprehensive review regarding the various dielectric integration schemes for emerging devices and their limitations with respect to ALD based methods along with a future outlook is provided. - Highlights: • We introduce various dielectric integration schemes for carbon-based devices. • Physical vapor deposition methods tend to degrade device performance. • Atomic layer deposition on pristine surfaces of graphene and nanotube is difficult. • We review different seeding techniques for atomic layer deposition of dielectrics. • Compare the performance of graphene top-gate devices with different dielectrics

Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.

Science.gov (United States)

Zavřel, Tomáš; Szabó, Milán; Tamburic, Bojan; Evenhuis, Christian; Kuzhiumparambil, Unnikrishnan; Literáková, Petra; Larkum, Anthony W D; Raven, John A; Červený, Jan; Ralph, Peter J

2018-04-01

This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P 700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO 2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation. Copyright © 2018 Elsevier B.V. All rights reserved.

Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

Science.gov (United States)

Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

2018-06-01

We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

Carbon/Hydrogen ratio determination in hydrocarbons and its mixtures by electron backscattering technique

International Nuclear Information System (INIS)

Padron, I.; Desdin, L.F.; Navarro, A.; Fuentes, M.

1996-01-01

A method carbon/hydrogen ratio (C/H) determination in hydrocarbons and its mixtures was improved using the electron backscattering technique. Besides the hetero atoms (S,O and N) influence in petroleum is studied for being able to determinate the C/H ratio in cuban petroleum with high sulphur contents

Nucleation of diamond by pure carbon ion bombardment--a transmission electron microscopy study

International Nuclear Information System (INIS)

Yao, Y.; Liao, M.Y.; Wang, Z.G.; Lifshitz, Y.; Lee, S.

2005-01-01

A cross-sectional high-resolution transmission electron microscopy (HRTEM) study of a film deposited by a 1 keV mass-selected carbon ion beam onto silicon held at 800 deg. C is presented. Initially, a graphitic film with its basal planes perpendicular to the substrate is evolving. The precipitation of nanodiamond crystallites in upper layers is confirmed by HRTEM, selected area electron diffraction, and electron energy loss spectroscopy. The nucleation of diamond on graphitic edges as predicted by Lambrecht et al. [W. R. L. Lambrecht, C. H. Lee, B. Segall, J. C. Angus, Z. Li, and M. Sunkara, Nature, 364 607 (1993)] is experimentally confirmed. The results are discussed in terms of our recent subplantation-based diamond nucleation model

Low Secondary Electron Yield Carbon Coatings for Electron-cloud Mitigation in Modern Particle Accelerators

CERN Document Server

Yin Vallgren, Christina; Calatroni, Sergio; Chiggiato, Paolo; Costa Pinto, Pedro; Marques, Hugo; Neupert, Holger; Taborelli, Mauro; Vollenberg, Wilhelmus; Wevers, Ivo; Yaqub, Kashif

2010-01-01

Electron-cloud is one of the main limitations for particle accelerators with positively charged beams of high intensity and short bunch spacing, as the SPS at CERN. The Secondary Electron Yield (SEY) of the inner surface of the vacuum chamber is the main parameter governing the phenomenon. The effect could be eliminated by coating the vacuum chambers with a material of low SEY, which does not require bake-out and is robust against air exposure. For such a purpose amorphous carbon (a-C) coatings were produced by magnetron sputtering of graphite targets. They exhibit maximum SEY between 0.95 and 1.05 after air transfer to the measuring instrument. After 1 month of air exposure the SEY rises by 10 - 20 % of the initial values. Storage in desiccator or by packaging in Al foil makes this increase negligible. The coatings have a similar X-ray photoelectron spectroscopy (XPS) C1s spectrum for a large set of deposition parameters and exhibit an enlarged linewidth compared to HOPG graphite. The static outgassing witho...

Radiative losses and electron cooling rates for carbon and oxygen plasma impurities

International Nuclear Information System (INIS)

Marchand, R.; Bonnin, X.

1992-01-01

Radiative losses and electron cooling rates are calculated for carbon and oxygen ions under conditions relevant to fusion plasmas. Both rates are calculated with the most recent recommended atomic data. A modified coronal model which includes the effects of metastable states is described and used to calculate the rates. Comparisons with other approaches are also discussed. (author). 36 ref, figs

Assessing and ameliorating the influence of the electron beam on carbon nanotube oxidation in environmental transmission electron microscopy

Energy Technology Data Exchange (ETDEWEB)

Koh, Ai Leen, E-mail: alkoh@stanford.edu [Stanford Nano Shared Facilities, Stanford University, Stanford, CA 94305 (United States); Sinclair, Robert [Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305 (United States)

2017-05-15

In this work, we examine how the imaging electron beam can induce damage in carbon nanotubes (CNTs) at varying oxygen gas pressures and electron dose rates using environmental transmission electron microscopy (ETEM). Our studies show that there is a threshold cumulative electron dose which brings about damage in CNTs in oxygen – through removal of their graphitic walls – which is dependent on O{sub 2} pressure, with a 4–5 fold decrease in total electron dose per decade increase at a lower pressure range (10{sup −6} to 10{sup −5} mbar) and approximately 1.3 –fold decrease per decade increase at a higher pressure range (10{sup −3} to 10{sup 0} mbar). However, at a given pressure, damage in CNTs was found to occur even at the lowest dose rate utilized, suggesting the absence of a lower limit for the latter parameter. This study provides guidelines on the cumulative dose required to damage nanotubes in the 10{sup −7} mbar to 10{sup 0} mbar pressure regimes, and discusses the role of electron dose rate and total electron dose on beam-induced CNT degradation experiments. - Highlights: • The electron beam ionizes gas molecules in ETEM and affects experimental outcomes. • Beam-induced damage in CNTs occurs at varying O{sub 2} pressures and electron dose rates. • There is a threshold cumulative dose to damage CNTs which depends on O{sub 2} pressure. • At a given pressure, CNT damage occurs even at the electron dose rate utilized.

Assessing and ameliorating the influence of the electron beam on carbon nanotube oxidation in environmental transmission electron microscopy

International Nuclear Information System (INIS)

Koh, Ai Leen; Sinclair, Robert

2017-01-01

In this work, we examine how the imaging electron beam can induce damage in carbon nanotubes (CNTs) at varying oxygen gas pressures and electron dose rates using environmental transmission electron microscopy (ETEM). Our studies show that there is a threshold cumulative electron dose which brings about damage in CNTs in oxygen – through removal of their graphitic walls – which is dependent on O_2 pressure, with a 4–5 fold decrease in total electron dose per decade increase at a lower pressure range (10"−"6 to 10"−"5 mbar) and approximately 1.3 –fold decrease per decade increase at a higher pressure range (10"−"3 to 10"0 mbar). However, at a given pressure, damage in CNTs was found to occur even at the lowest dose rate utilized, suggesting the absence of a lower limit for the latter parameter. This study provides guidelines on the cumulative dose required to damage nanotubes in the 10"−"7 mbar to 10"0 mbar pressure regimes, and discusses the role of electron dose rate and total electron dose on beam-induced CNT degradation experiments. - Highlights: • The electron beam ionizes gas molecules in ETEM and affects experimental outcomes. • Beam-induced damage in CNTs occurs at varying O_2 pressures and electron dose rates. • There is a threshold cumulative dose to damage CNTs which depends on O_2 pressure. • At a given pressure, CNT damage occurs even at the electron dose rate utilized.

Characterization of electron beam evaporated carbon films and compound formation on titanium and silicon

International Nuclear Information System (INIS)

Luthin, J.; Linsmeier, C.

2001-01-01

The formation of carbon-based mixed materials is unavoidable on the plasma-facing components (e.g. first wall and divertor) of fusion devices when carbon is used together with other materials. On the surfaces of these components very different conditions with respect to particle and energy impact occur. To predict the mixed material formation under these conditions the precise knowledge of the fundamental mechanisms governing these interactions is essential. In this paper we present the results of carbon interaction with titanium and silicon, as model substances for metallic and covalent carbides, during thermal treatment. To perform basic studies of the reactions of carbon with different elements, thin carbon films are produced by electron beam evaporation on the different substrates under UHV conditions. All measurements for chemical analysis are performed using X-ray photoelectron spectroscopy (XPS). We discuss first the properties of the deposited carbon films. The carbon films are characterized on inert gold surfaces and are compared to bulk graphite. Annealing of the carbon films up to 970 K leads to a transition from a disordered carbon network into a graphitic structure. Preparation of carbon films at room temperature on titanium or silicon leads to a limited carbide formation at the carbon/substrate interface. Carbon deposited in excess of several monolayers is present in elementary form. Annealing of the samples leads to complete carbidization consuming the available carbon in both cases. Titanium reacts to TiC and additional substoichiometric carbide, silicon forms SiC with exact stoichiometry. (orig.)

Electronic structure and field emission properties of nitrogen doped graphene nano-flakes (GNFs:N) and carbon nanotubes (CNTs:N)

Energy Technology Data Exchange (ETDEWEB)

Ray, Sekhar C., E-mail: Raysc@unisa.ac.za [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Private Bag X6, Florida, 1710, Science Campus, Christiaan de Wet and Pioneer Avenue, Florida Park, Johannesburg (South Africa); Pong, W.F. [Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan (China); Papakonstantinou, P. [Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster, Shore Road, Newtownabbey BT37 0QB (United Kingdom)

2016-09-01

Highlights: • Nitrogen doped graphene nano-flakes (GNFs:N) and carbon nano-tubes (CNTs:N) are used to study the electronic/bonding structure along with their defects state. • The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy used for the study of the defects states of CNTs:N than GNFs:N. • The electron field emission result shows that the turn on electric field is lower in case of CNTs:N than GNFs:N. • All results are good agreement with XANES and the results obtained from Raman spectra. - Abstract: Substitution of hetero-atom doping is a promising route to modulate the outstanding material properties of carbon nanotubes and graphene for customized applications. Nitrogen-doping has been introduced to ensure tunable work-function, enhanced n-type carrier concentration, diminished surface energy, and manageable polarization. Along with the promising assessment of N-doping effects, research on the N-doped carbon based composite structures is emerging for the synergistic integration with various functional materials. Nitrogen undoped/doped graphene nano-flakes (GNFs/GNFs:N) and multiwall carbon nano-tubes (MWCNTs/MWCNTs:N) are used for comparative study of their electronic/bonding structure along with their defects state. X-ray absorption near edge structure (XANES) spectroscopy shows that the GNFs:N produce mainly pyridine like structure; whereas MWCNTs:N shows graphitic nitrogen atoms are attached with the carbon lattice. The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy shows that the defects is higher in MWCNTs:N than GNFs:N. The electron field emission result shows that the turn on electric field is lower (higher electron emission current) in case of MWCNTs:N than GNFs:N and are good agreement with XANES and the results obtained from Raman spectra.

Structural, electronic and photovoltaic characterization of multiwalled carbon nanotubes grown directly on stainless steel

Directory of Open Access Journals (Sweden)

Luca Camilli

2012-05-01

Full Text Available We have taken advantage of the native surface roughness and the iron content of AISI-316 stainless steel to grow multiwalled carbon nanotubes (MWCNTs by chemical vapour deposition without the addition of an external catalyst. The structural and electronic properties of the synthesized carbon nanostructures have been investigated by a range of electron microscopy and spectroscopy techniques. The results show the good quality and the high graphitization degree of the synthesized MWCNTs. Through energy-loss spectroscopy we found that the electronic properties of these nanostructures are markedly different from those of highly oriented pyrolytic graphite (HOPG. Notably, a broadening of the π-plasmon peak in the case of MWCNTs is evident. In addition, a photocurrent was measured when MWCNTs were airbrushed onto a silicon substrate. External quantum efficiency (EQE and photocurrent values were reported both in planar and in top-down geometry of the device. Marked differences in the line shapes and intensities were found for the two configurations, suggesting that two different mechanisms of photocurrent generation and charge collection are in operation. From this comparison, we are able to conclude that the silicon substrate plays an important role in the production of electron–hole pairs.

Stress corrosion cracking tests on electron beam welded carbon steel specimens in carbonate-bicarbonate solution

International Nuclear Information System (INIS)

Parkins, R.N.

1985-04-01

Stress corrosion cracking tests have been performed on tapered carbon steel test pieces containing electron beam welds with a view to defining susceptibility to such cracking in a carbonate-bicarbonate solution at 90 C and an appropriate electrode potential. The tests involved applying cyclic loads to the specimens and it is shown that the threshold stress for cracking reduces linearly with increase in the magnitude of the cyclic load component. Extrapolation of these trends to zero fluctuating stress indicates static load threshold stresses in the vicinity of the yield stress (i.e. about 300 N/mm 2 for parent plate without a weld, 400 N/mm 2 for specimens with welds on one side only and 600 N/mm 2 for specimens having welds penetrating through the thickness of the specimen). The averages of the maximum crack velocities observed were least for parent plate material and greatest for weld metal, the former being essentially intergranular in morphology and the latter mostly transgranular, with heat affected zone material being intermediate between these extremes. (author)

Perpendicular State of an Electronically Excited Stilbene: Observation by Femtosecond-Stimulated Raman Spectroscopy.

Science.gov (United States)

Quick, Martin; Dobryakov, Alexander L; Ioffe, Ilya N; Granovsky, Alex A; Kovalenko, Sergey A; Ernsting, Nikolaus P

2016-10-20

In the photoisomerization path of stilbene, a perpendicular state P on the S 1 potential energy surface is expected just before internal conversion through a conical intersection S 1 /S 0 . For decades the observation of P was thwarted by a short lifetime τ P in combination with slow population flow over a barrier. But these limitations can be overcome by ethylenic substitution. Following optical excitation of trans-1,1'-dicyanostilbene, P is populated significantly (τ P = 27 ps in n-hexane) and monitored by an exited-state absorption band at 370 nm. Here we report stimulated Raman lines of P. The strongest, at 1558 cm -1 , is attributed to stretching vibrations of the phenyl rings. Transient electronic states, resonance conditions, and corresponding Raman signals are discussed.

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

Science.gov (United States)

Raitt, W. J.; Banks, P. M.; Denig, W. F.; Anderson, H. R.

1982-01-01

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

International Nuclear Information System (INIS)

Raitt, W.J.; Banks, P.M.

1982-01-01

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon. 5 references

Improving Single-Carbon-Nanotube-Electrode Contacts Using Molecular Electronics.

Science.gov (United States)

Krittayavathananon, Atiweena; Ngamchuea, Kamonwad; Li, Xiuting; Batchelor-McAuley, Christopher; Kätelhön, Enno; Chaisiwamongkhol, Korbua; Sawangphruk, Montree; Compton, Richard G

2017-08-17

We report the use of an electroactive species, acetaminophen, to modify the electrical connection between a carbon nanotube (CNT) and an electrode. By applying a potential across two electrodes, some of the CNTs in solution occasionally contact the electrified interface and bridge between two electrodes. By observing a single CNT contact between two microbands of an interdigitated Au electrode in the presence and absence of acetaminophen, the role of the molecular species at the electronic junction is revealed. As compared with the pure CNT, the current magnitude of the acetaminophen-modified CNTs significantly increases with the applied potentials, indicating that the molecule species improves the junction properties probably via redox shuttling.

Experimental electrical stimulation of the bladder using a new device

DEFF Research Database (Denmark)

Petersen, T.; Christiansen, P.; Nielsen, B.

1986-01-01

Repeated bladder contractions were evoked during a six month period in three unanaesthetized female minipigs by using unipolar carbon fiber electrodes embedded in the bladder wall adjacent to the ureterovesical junction. In contrast to bipolar and direct bladder muscle stimulation unipolar...... electrodes at each ureterovesical junction evoked bladder pressure increase similar to those produced in previous investigations in dogs. Sacral nerve stimulation of S2 evoked bladder contraction at a minimal current. Microscopic examination revealed no cellular reactions to the carbon fibers...

Elevated moisture stimulates carbon loss from mineral soils by releasing protected organic matter.

Science.gov (United States)

Huang, Wenjuan; Hall, Steven J

2017-11-24

Moisture response functions for soil microbial carbon (C) mineralization remain a critical uncertainty for predicting ecosystem-climate feedbacks. Theory and models posit that C mineralization declines under elevated moisture and associated anaerobic conditions, leading to soil C accumulation. Yet, iron (Fe) reduction potentially releases protected C, providing an under-appreciated mechanism for C destabilization under elevated moisture. Here we incubate Mollisols from ecosystems under C 3 /C 4 plant rotations at moisture levels at and above field capacity over 5 months. Increased moisture and anaerobiosis initially suppress soil C mineralization, consistent with theory. However, after 25 days, elevated moisture stimulates cumulative gaseous C-loss as CO 2 and CH 4 to >150% of the control. Stable C isotopes show that mineralization of older C 3 -derived C released following Fe reduction dominates C losses. Counter to theory, elevated moisture may significantly accelerate C losses from mineral soils over weeks to months-a critical mechanistic deficiency of current Earth system models.

Stimulation of methanogenesis in anaerobic digesters treating leachate from a municipal solid waste incineration plant with carbon cloth.

Science.gov (United States)

Lei, Yuqing; Sun, Dezhi; Dang, Yan; Chen, Huimin; Zhao, Zhiqiang; Zhang, Yaobin; Holmes, Dawn E

2016-12-01

Bio-methanogenic digestion of incineration leachate is hindered by high OLRs, which can lead to build-up of VFAs, drops in pH and ultimately in reactor souring. It was hypothesized that incorporation of carbon cloth into reactors treating leachate would promote DIET and enhance reactor performance. To examine this possibility, carbon cloth was added to laboratory-scale UASB reactors that were fed incineration leachate. As expected, the carbon-cloth amended reactor could operate stably with a 34.2% higher OLR than the control (49.4 vs 36.8kgCOD/(m 3 d)). Microbial community analysis showed that bacteria capable of extracellular electron transfer and methanogens known to participate in DIET were enriched on the carbon cloth surface, and conductivity of sludge from the carbon cloth amended reactor was almost twofold higher than sludge from the control (9.77 vs 5.47μS/cm), suggesting that microorganisms in the experimental reactor may have been expressing electrically conductive filaments. Copyright © 2016 Elsevier Ltd. All rights reserved.

The characteristics of carbon nanotubes grown at low temperature for electronic device application

Energy Technology Data Exchange (ETDEWEB)

Park, Yong Seob [Department of Photoelectronics Information, Chosun College of Science and Technology, Gwangju (Korea, Republic of); Yi, Junsin [School of Information and Communications Engineering, Sungkyunkwan University, Suwon, 440–746 (Korea, Republic of); Lee, Jaehyeong, E-mail: jaehyeong@skku.edu [School of Information and Communications Engineering, Sungkyunkwan University, Suwon, 440–746 (Korea, Republic of)

2013-11-01

For the application of carbon nanotubes (CNTs) in flexible electronic devices, the CNTs were grown on Corning 1737 glass substrate by microwave plasma enhanced chemical vapor deposition (MPECVD) method. To deposit the catalyst layer, TiN buffer layer of 200 nm thickness and Ni catalyst layer of 60 nm were first deposited on the glass by r.f. magnetron sputtering method. The CH{sub 4} and H{sub 2} gases are used as the synthesis gas of CNTs and the working pressure was about 2.13 kPa, and the substrate bias was about − 200 V. The growth time was from 2 min to 5 min and the microwave power was about 800 W. The substrate temperature as the main parameter was changed from 400 °C to 550 °C. The structural properties of CNTs synthesized with the substrate temperature were investigated using Raman, field emission scanning electron microscopy, and transmission electron microscopy methods. The surface and electrical properties of CNTs grown by MPECVD method were studied by scanning probe microscopy and four-point probe methods. We obtained the multi-walled CNTs (MW-CNTs). Multi-walled CNTs were vertically grown on Ni/TiN/glass substrates below 500 °C without any glass deformations. As the substrate temperature was increased, the crystallinity of CNTs was improved. Ni catalyst was found at the tip of CNT by the TEM observation and the grown CNTs were found to have a multi-walled with bamboo like structure. - Highlights: • Synthesis of vertically aligned carbon nanotubes. • Effects of substrate temperature on carbon nanotubes properties. • Improvement of the crystallinity with increasing substrate temperature. • Reduction of sheet resistance with increasing substrate temperature.

Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB{sub 2} superconductor nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Bateni, Ali; Somer, Mehmet, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr [Department of Chemistry, Koc University, RumelifeneriYolu, Sariyer, Istanbul (Turkey); Erdem, Emre, E-mail: emre.erdem@physchem.uni-freiburg.de, E-mail: msomer@ku.edu.tr; Repp, Sergej; Weber, Stefan [Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 21, 79104 Freiburg (Germany); Acar, Selcuk; Kokal, Ilkin [Pavezyum Kimya Sanayi Dış Ticaret LTD. ŞTI., Tuzla, Istanbul (Turkey); Häßler, Wolfgang [Leibniz Institute for Solid State and Materials Research Dresden (IFW), P.O. Box 270116, 01171 Dresden (Germany)

2015-04-21

Undoped and carbon-doped magnesium diboride (MgB{sub 2}) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB{sub 2} samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp{sup 3}-hybridized carbon radicals were detected. A strong reduction in the critical temperature T{sub c} was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra.

First-principles study of electronic structure of deformed carbon nanotubes

Directory of Open Access Journals (Sweden)

Kazuchika Iwami, Hidekazu Goto, Kikuji Hirose and Tomoya Ono

2007-01-01

Full Text Available On the basis of density functional theory, we study the electronic structures of five types of carbon nanotubes: the non-deformed (6,6 tube, the uniformly stretched tube along the tube axis, the uniformly compressed tube, the partially stretched tube and the partially compressed tube. The electron charge density increases at the compressed C–C bond of the partially stretched tube, while the density decreases at the stretched C–C bond of the partially stretched tube. In addition, the a1 and e1 states of the (6,6 tube contribute to the bonding along the tube axis and the a2 and e2 states are the bonds connecting the atoms in the same layers. Thus, the energy bands of the a1 and e1 states are sensitively affected by the deformation of the tubes along the tube axis.

Electron Processing at 50 eV of Terphenylthiol Self-Assembled Monolayers: Contributions of Primary and Secondary Electrons.

Science.gov (United States)

Houplin, Justine; Dablemont, Céline; Sala, Leo; Lafosse, Anne; Amiaud, Lionel

2015-12-22

Aromatic self-assembled monolayers (SAMs) can serve as platforms for development of supramolecular assemblies driven by surface templates. For many applications, electron processing is used to locally reinforce the layer. To achieve better control of the irradiation step, chemical transformations induced by electron impact at 50 eV of terphenylthiol SAMs are studied, with these SAMs serving as model aromatic SAMs. High-resolution electron energy loss spectroscopy (HREELS) and electron-stimulated desorption (ESD) of neutral fragment measurements are combined to investigate electron-induced chemical transformation of the layer. The decrease of the CH stretching HREELS signature is mainly attributed to dehydrogenation, without a noticeable hybridization change of the hydrogenated carbon centers. Its evolution as a function of the irradiation dose gives an estimate of the effective hydrogen content loss cross-section, σ = 2.7-4.7 × 10(-17) cm(2). Electron impact ionization is the major primary mechanism involved, with the impact electronic excitation contributing only marginally. Therefore, special attention is given to the contribution of the low-energy secondary electrons to the induced chemistry. The effective cross-section related to dissociative secondary electron attachment at 6 eV is estimated to be 1 order of magnitude smaller. The 1 eV electrons do not induce significant chemical modification for a 2.5 mC cm(-2) dose, excluding their contribution.

Scanning electron microscopy characterisation of carbon deposited layers in Tore Supra

International Nuclear Information System (INIS)

Delchambre, E.; Brosset, C.; Reichle, R.; Devynck, P.; Guirlet, R.; Tsitrone, E.; Saikali, W.; Dominici, C.; Charai, A.

2003-01-01

For long discharges in Tore-Supra, an infra-red safety system has been installed to survey surface temperature of the target plates located below the toroidal pump limiter. A shift in temperature is attributed to the growth of a carbon layer at the surface of the neutralizer and has been estimated to a temperature increase of 400 Celsius degrees between virgin and layered surfaces. For temperature safety analysis, target plates have been cleaned and carbon layers were sampled for scanning electronic microscopy (SEM) study. SEM micrographs have allowed to measure the deposited layer thickness and to study the specific fractal and stratified structure. Energy dispersive X-ray spectroscopy analysis has permitted to distinguish carbon layers corresponding to boronization and then to deduce an average growth rate of about 20 nm/s. The growth rate is not constant and is likely to depend on plasma operation parameters. These analyses completed by time of flight secondary ions mass spectrometry (ToF-SIMS) have shown a beneficial effect of the boronization on metallic contamination of the plasma, confirming the in situ optical spectroscopic measurements. These analyses have also shown an increase of hydrogen storage in carbon layer due to boronization. Although the measurements performed on deposited layer are very local, the results reflect the history of the 2002 campaign. (A.C.)

Polymer-carbon black composite sensors in an electronic nose for air-quality monitoring

Science.gov (United States)

Ryan, M. A.; Shevade, A. V.; Zhou, H.; Homer, M. L.

2004-01-01

An electronic nose that uses an array of 32 polymer-carbon black composite sensors has been developed, trained, and tested. By selecting a variety of chemical functionalities in the polymers used to make sensors, it is possible to construct an array capable of identifying and quantifying a broad range of target compounds, such as alcohols and aromatics, and distinguishing isomers and enantiomers (mirror-image isomers). A model of the interaction between target molecules and the polymer-carbon black composite sensors is under development to aid in selecting the array members and to enable identification of compounds with responses not stored in the analysis library.

Spinning Carbon Nanotube Nanothread under a Scanning Electron Microscope

Directory of Open Access Journals (Sweden)

Mark Schulz

2011-08-01

Full Text Available Nanothread with a diameter as small as one hundred nanometers was manufactured under a scanning electron microscope. Made directly from carbon nanotubes, and inheriting their superior electrical and mechanical properties, nanothread may be the world’s smallest man-made fiber. The smallest thread that can be spun using a bench-top spinning machine is about 5 microns in diameter. Nanothread is a new material building block that can be used at the nanoscale or plied to form yarn for applications at the micro and macro scales. Preliminary electrical and mechanical properties of nanothread were measured. The resistivity of nanothread is less than 10−5 Ω∙m. The strength of nanothread is greater than 0.5 GPa. This strength was obtained from measurements using special glue that cures in an electron microscope. The glue weakened the thread, thus further work is needed to obtain more accurate measurements. Nanothread will have broad applications in enabling electrical components, circuits, sensors, and tiny machines. Yarn can be used for various macroscale applications including lightweight antennas, composites, and cables.

Evidence of hot spot formation on carbon limiters due to thermal electron emission

International Nuclear Information System (INIS)

Philipps, V.; Samm, U.; Tokar, M.Z.; Unterberg, B.; Pospieszczyk, A.; Schweer, B.

1993-01-01

Carbon test limiters have been exposed in TEXTOR to high heat loads up to about 30 MW/m 2 . The evolutions of the surface temperature distribution and of the carbon release have been observed by means of local diagnostics. A sudden acceleration of the rise of the surface temperature has been found at a critical temperature of approx. 2400 deg. C. The increase of the rate of the temperature rise is consistent with an enhancement of the power loading by a factor of 2.5-3. Following the temperature jump (hot spot), a quasi-equilibrium temperature establishes at approx. 2700 deg. C. The development of the hot spot is explained by an increase of the local power loading to the breakdown of the sheath potential by thermal emission of electrons from the carbon surface. Simultaneously with the appearance of the hot spot, the carbon release from the surface increases sharply. This increase can be explained by normal thermal sublimation. Sublimation cooling contributes to the establishment of the quasi-equilibrium temperature at about 2700 deg. C. (author). 16 refs, 10 figs

Scanning and transmission electron microscopy investigation of multiwall carbon nanotube/nickel oxide nanocomposite thin films

CSIR Research Space (South Africa)

Roro, Kittessa T

2011-12-01

Full Text Available Owing to their unique electronic and optical properties, nanocomposite thin films are widely used for converting solar radiation therapy into other conventional energy forms, such as heat and electricity. Carbon nanotube-based composites which can...

Metagenomic insight into methanogenic reactors promoting direct interspecies electron transfer via granular activated carbon.

Science.gov (United States)

Park, Jeong-Hoon; Park, Jong-Hun; Je Seong, Hoon; Sul, Woo Jun; Jin, Kang-Hyun; Park, Hee-Deung

2018-07-01

To provide insight into direct interspecies electron transfer via granular activated carbon (GAC), the effect of GAC supplementation on anaerobic digestion was evaluated. Compared to control samples, the GAC supplementation increased the total amount of methane production and its production rate by 31% and 72%, respectively. 16S rDNA sequencing analysis revealed a shift in the archaeal community composition; the Methanosarcina proportion decreased 17%, while the Methanosaeta proportion increased 5.6%. Metagenomic analyses based on shotgun sequencing demonstrated that the abundance of pilA and omcS genes belonging to Geobacter species decreased 69.4% and 29.4%, respectively. Furthermore, the analyses suggested a carbon dioxide reduction pathway rather than an acetate decarboxylation pathway for methane formation. Taken together, these results suggest that GAC improved methane production performance by shifting the microbial community and altering functional genes associated with direct interspecies electron transfer via conductive materials. Copyright © 2018 Elsevier Ltd. All rights reserved.

Non-uniform shrinkage of multiple-walled carbon nanotubes under in situ electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Li, Lunxiong [South China Normal University, Brain Science Institute, Guangzhou (China); Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China); Su, Jiangbin [Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China); Chang Zhou University, School of Mathematics and Physics, Changzhou (China); Zhu, Xianfang [Xiamen University, China-Australia Joint Laboratory for Functional Nanomaterials and Physics Department, Xiamen (China)

2016-10-15

Instability of multiple-walled carbon nanotubes (MWCNTs) was investigated by in situ transmission electron microscopy at room temperature. Specially, the non-uniform shrinkage of tubes was found: The pristine MWCNT shrank preferentially in its axial direction from the most curved free cap end of the tube, but the shrinkage of the tube diameter was offset by the axial shrinkage: For the complex MWCNT, the two inner MWCNTs also preferentially axially shrank from their most curved cap ends and separated from each other. However, for the effect of the radial pressure from the out walls which enveloped the two inner tubes and the tube amorphization, the two inner tubes were extruded to come close to each other and finally touched again. The new ''evaporation'' and ''diffusion'' mechanisms of carbon atoms as driven by the nano-curvature of CNT and the electron beam-induced athermal activation were suggested to explain the above phenomena. (orig.)

Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

Energy Technology Data Exchange (ETDEWEB)

Dixon, David Adams [The University of Alabama

2013-07-02

This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

Growth, characterisation and electronic applications of amorphous hydrogenated carbon

International Nuclear Information System (INIS)

Paul, S.

2000-11-01

My thesis proposes solutions to a number of riddles associated with the material, hydrogenated amorphous carbon, (a-C:H). This material has lately generated interest in the electronic engineering community, owing to some remarkable properties. The characterisation of amorphous carbon films, grown by radio frequency plasma enhanced chemical vapour deposition has been reported. The coexistence of multiple phases in the same a-C:H film manifests itself in the inconsistent electrical behaviour of different parts of the film, thus rendering it difficult to predict the nature of films. For the first time, in this thesis, a reliable prediction of Schottky contact formation on a-C:H films is reported. A novel and simple development on a Scanning Electron Microscope, configured to study the electrical properties of the grown a-C:H films, has been reported. Since device performance is crucially linked to the density of states in the film, a study of the same was undertaken in my doctoral research. I present a mathematical formalism to estimate the density of states in a-C:H. The most commonly used metal, (aluminium), for contact formation on a-C:H films, has been concluded to be the least suitable. On the basis of the study presented in this thesis, copper and chromium are judged to be the best alternatives. The resilience of a-C:H/Si heterostructures under high voltages (upto 900 V) has been reported in this thesis for the first time. The performance of a-C:H grown at room temperature on GaAs, has been studied and concluded to be satisfactory on the basis of good adherence and low leakage currents. Such a structure was motivated by the applicability in Metal Insulator Semiconductor Field Effect Transistors (MISFET). (author)

Electron density as the main parameter influencing the formation of fullerenes in a carbon plasma

International Nuclear Information System (INIS)

Churilov, G.N.; Bulina, N.V.; Novikov, P.V.; Lopatin, V.A.; Vnukova, N.G.; Bachilo, S.M.; Tsyboulski, D.; Weisman, R.B.

2002-01-01

Thermodynamic estimates are presented for the formation of spheroidal and flat carbon clusters from reactant species of different charges. Charge is shown to strongly influence the geometry and stability of flat clusters. Changes in the charge of flat clusters can promote both their folding to spheroidal structures and their dissociation. It is concluded that the fluctuations of electron concentration in carbon plasma can result in the accumulation of fullerene clusters and the dissociation of flat clusters. Computer simulations of fullerene C 60 formation from carbon clusters having different charges are carried out using the program HyperChem 5 to calculate the optimal geometry of molecules and their molecular dynamics at different temperatures [ru

Recent development of carbon nanotube

Energy Technology Data Exchange (ETDEWEB)

Yamabe, Tokio [Div. of Molecular Engineering, Kyoto Univ. (Japan); [Inst. for Fundamental Chemistry, Kyoto (Japan)

1995-03-15

Recent developments of carbon nanotubes are reviewed. Analytical solutions for the electronic structure of carbon nanotube on the basis of thight-binding approximation are presented and interpreted using the concepts of crystal orbital. The electronic properties of actual carbon nanotubes are presented. The electronic structures of carbon nanotubes in the presence of magnetic fiels are also summerized. (orig.)

Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A., E-mail: guirado@ifisica.uaslp.mx [Instituto de Física “Manuel Sandoval Vallarta,” Universidad Autónoma de San Luis Potosí, Álvaro Obregón 64, 78000 San Luis Potosí, San Luis Potosí (Mexico); Gámez-Corrales, R. [Departamento de Física, Universidad de Sonora, Apartado Postal 5-088, 83190, Hermosillo, Sonora (Mexico)

2014-11-07

We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

Arbuscular mycorrhizal fungi increase organic carbon decomposition under elevated carbon dioxide

Science.gov (United States)

A major goal of climate change research is to understand whether and how terrestrial ecosystems can sequester more carbon to mitigate rising atmospheric carbon dioxide (CO2) levels. The stimulation of arbuscular mycorrhizal fungi (AMF) by elevated atmospheric CO2 has been assumed to be a major mecha...

Direct electron transfer and electrocatalysis of glucose oxidase immobilized on glassy carbon electrode modified with Nafion and mesoporous carbon FDU-15

International Nuclear Information System (INIS)

Wang Kunqi; Yang Hua; Zhu Lin; Ma Zhongsu; Xing Shenyang; Lv Qiang; Liao Jianhui; Liu Changpeng; Xing Wei

2009-01-01

In this paper, it was found that glucose oxidase (GOD) has been stably immobilized on glassy carbon electrode modified with mesoporous carbon FDU-15 (MC-FDU-15) and Nafion by simple technique. The sorption behavior of GOD immobilized on MC-FDU-15 matrix was characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV-vis), FTIR, respectively, which demonstrated that MC-FDU-15 could facilitate the electron exchange between the active center of GOD and electrode. The direct electrochemistry and electrocatalysis behavior of GOD on the modified electrode were characterized by cyclic voltammogram (CV) which indicated that GOD immobilized on Nafion and MC-FDU-15 matrices display direct, reversible and surface-controlled redox reaction with an enhanced electron transfer rate constant of 4.095 s -1 in 0.1 M phosphate buffer solution (PBS) (pH 7.12). Furthermore, it was also discovered that, in the presence of O 2 , GOD immobilized on Nafion and MC-FDU-15 matrices could produce a linear response to glucose. Thus, Nafion/GOD-MC-FDU-15/GC electrode is hopeful to be used in glucose biosensor. In addition, GOD immobilized on MC-FDU-15 and Nafion matrices possesses an excellent bioelectrocatalytic activity for the reduction of O 2 . So, the Nafion/GOD-MC-FDU-15/GC electrode can be utilized as the cathode in biofuel cell.

Particle trapping in stimulated scattering processes

International Nuclear Information System (INIS)

Karttunen, S.J.; Heikkinen, J.A.

1981-01-01

Particle trapping effects on stimulated Brillouin and Raman scattering are investigated. A time and space dependent model assumes a Maxwellian plasma which is taken to be homogeneous in the interaction region. Ion trapping has a rather weak effect on stimulated Brillouin scattering and large reflectivities are obtained even in strong trapping regime. Stimulated Raman scattering is considerably reduced by electron trapping. Typically 15-20 times larger laser intensities are required to obtain same reflectivity levels than without trapping. (author)

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Energy Technology Data Exchange (ETDEWEB)

Li, X.; Nilsson, D.; Danielsson, Ö.; Pedersen, H.; Janzén, E.; Forsberg, U. [Department of Physics, Chemistry, and Biology (IFM), Linköping University, Linköping 58183 (Sweden); Bergsten, J.; Rorsman, N. [Microwave Electronics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg 41296 (Sweden)

2015-12-28

The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) epitaxial layer closest to the substrate and a lower doped layer (3 × 10{sup 16 }cm{sup −3}) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 10{sup 18 }cm{sup −3}) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

Contribution to the study of solvated electrons in water and alcohols and of radiolytic processes in organic carbonates by picosecond pulse radiolysis

International Nuclear Information System (INIS)

Torche, Faycal

2012-01-01

This work is part of the study area of the interaction of radiation with polar liquids. Using the picosecond electron accelerator ELYSE, studies were conducted using the techniques of pulse radiolysis combined with absorption spectrophotometry Time-resolved in the field of a picosecond. This work is divided into two separate chapters. The first study addresses the temporal variation of the radiolytic yield of solvated electron in water and simple alcohols. Due to original detection system mounted on the accelerator ELYSE, composed of a flash lamp specifically designed for the detection and a streak-camera used for the first time in absorption spectroscopy, it was possible to record the time-dependent radiolytic yields of the solvated electron from ten picoseconds to a few hundred nanoseconds. The scavenging of the electron solvated by methyl viologen, was utilized to reevaluate the molar extinction coefficient of the absorption spectrum of solvated electron in water and ethanol from isobestic points which corresponds to the intersection of the absorption spectra of solvated electron which disappears and methyl viologen which is formed during the reaction. The second chapter is devoted to the study of liquid organic carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). This family of carbonate which compose the electrolytes lithium batteries, has never been investigated by pulse radiolysis. The studies were focused on the PC in the light of these physicochemical characteristics, including its very high dielectric constant and its strong dipole moment of 4.9 D. The first results were obtained on aqueous solutions containing propylene carbonate to observe the reactions of reduction and oxidation of PC by radiolytic species of water (solvated electron and OH radicals). Then, after the identification (spectral and kinetic) of the species formed by interaction with the OH radical as the PC* radical resulting from the

THE STIMULATING EFFECT OF LASER RED LIGHT, FAR RED LIGHT AND SODIUM CARBONATE AT THE INITIAL STAGES OF BARLEY ONTOGENESIS

Directory of Open Access Journals (Sweden)

G. P. Dudin

2014-01-01

Full Text Available Summary. Modern ecological state of the environment and human unhealthy diet cause many diseases. A healthy diet is the one that contains adequate amounts of proteins, fats, carbohydrates, vitamins, macronutrients and micronutrients. Photosynthesis i. e. the process by which plants produce organic compounds from carbon dioxide and water, is the source of life, the source of evolution and proliferation of life forms on the Earth. Thus, the juice made from sprouted barley provides physiologically active chlorophyll, macronutrients and micronutrients, vitamins А, В2 , В3 , В5 , В6 , В8 , Е and К. It is well known that light from a red laser with a wavelength of 638.2 nm has a stimulating action on the germination energy, germination ability and productivity of seeds, and on the crop yields. Therefore, this research is of primary importance today. The research result produced a sharp decline in plant vigor and germinating capacity of barley when soaking in 1n sodium carbonate solution, as well as changes in the ratio of potassium-sodium balance in plants. Thus at lower concentrations of sodium carbonate and 0.1 n sodium increasing of pigment content in barley is observed on the seventh day. The red laser light has a similar stimulating action: the chlorophyll content of barley plants increased after the red laser treatment of barley seeds. However, the chlorophyll contents were depressed when the seeds were exposed to far red light with wavelengths of 754±10 nm. Using these factors, one can manage the content of chlorophyll and sodium-potassium balance in the initial stages of barley ontogenesis in the technology of barley juice or the powder for a healthy and proper human diet.

Stimulated coherent transition radiation

International Nuclear Information System (INIS)

Hung-chi Lihn.

1996-03-01

Coherent radiation emitted from a relativistic electron bunch consists of wavelengths longer than or comparable to the bunch length. The intensity of this radiation out-numbers that of its incoherent counterpart, which extends to wavelengths shorter than the bunch length, by a factor equal to the number of electrons in the bunch. In typical accelerators, this factor is about 8 to 11 orders of magnitude. The spectrum of the coherent radiation is determined by the Fourier transform of the electron bunch distribution and, therefore, contains information of the bunch distribution. Coherent transition radiation emitted from subpicosecond electron bunches at the Stanford SUNSHINE facility is observed in the far-infrared regime through a room-temperature pyroelectric bolometer and characterized through the electron bunch-length study. To measure the bunch length, a new frequency-resolved subpicosecond bunch-length measuring system is developed. This system uses a far-infrared Michelson interferometer to measure the spectrum of coherent transition radiation through optical autocorrelation with resolution far better than existing time-resolved methods. Hence, the radiation spectrum and the bunch length are deduced from the autocorrelation measurement. To study the stimulation of coherent transition radiation, a special cavity named BRAICER is invented. Far-infrared light pulses of coherent transition radiation emitted from electron bunches are delayed and circulated in the cavity to coincide with subsequent incoming electron bunches. This coincidence of light pulses with electron bunches enables the light to do work on electrons, and thus stimulates more radiated energy. The possibilities of extending the bunch-length measuring system to measure the three-dimensional bunch distribution and making the BRAICER cavity a broadband, high-intensity, coherent, far-infrared light source are also discussed

Carbon Micronymphaea: Graphene on Vertically Aligned Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Jong Won Choi

2013-01-01

Full Text Available This paper describes the morphology of carbon nanomaterials such as carbon nanotube (CNT, graphene, and their hybrid structure under various operating conditions during a one-step synthesis via plasma-enhanced chemical vapor deposition (PECVD. We focus on the synthetic aspects of carbon hybrid material composed of heteroepitaxially grown graphene on top of a vertical array of carbon nanotubes, called carbon micronymphaea. We characterize the structural features of this unique nanocomposite by uses of electron microscopy and micro-Raman spectroscopy. We observe carbon nanofibers, poorly aligned and well-aligned vertical arrays of CNT sequentially as the growth temperature increases, while we always discover the carbon hybrids, called carbon micronymphaea, at specific cooling rate of 15°C/s, which is optimal for the carbon precipitation from the Ni nanoparticles in this study. We expect one-pot synthesized graphene-on-nanotube hybrid structure poses great potential for applications that demand ultrahigh surface-to-volume ratios with intact graphitic nature and directional electronic and thermal transports.

Electron-Stimulated Desorption of Positive Ions from Methanol Adsorbed on a Solid Ar Substrate

Science.gov (United States)

Kawanowa, H.; Hanatani, K.; Gotoh, Y.; Souda, R.

Electron-stimulated desorption (ESD) of positive ions from weakly physisorbed molecules has been investigated. From methanol adsorbed on a solid Ar substrate, the protonated cluster ions of the type H+(CH3OH)n (n = 1 - 4) are emitted, together with the fragment ions such as CHn+ (n = 0 - 3), H3O+, CHO+, CH3O+, etc. The yields of these ions are markedly enhanced at the smallest coverage and decay steeply with increasing coverage. Coulomb explosion between valence holes confined in adsorbed nanoclusters is responsible for the enhanced ion yields. Very few ions except for H+ are emitted from a thick layer as well as nanoclusters adsorbed directly on a metal substrate due to the delocalization of valence holes.

Effects of different external carbon sources and electron acceptors on interactions between denitrification and phosphorus removal in biological nutrient removal processes.

Science.gov (United States)

Hu, Xiang; Sobotka, Dominika; Czerwionka, Krzysztof; Zhou, Qi; Xie, Li; Makinia, Jacek

The effects of two different external carbon sources (acetate and ethanol) and electron acceptors (dissolved oxygen, nitrate, and nitrite) were investigated under aerobic and anoxic conditions with non-acclimated process biomass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/(g MLVSS·h) (MLVSS: mixed liquor volatile suspended solids), respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO 2 -N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher denitrification rates were obtained with acetate (1.4 and 0.8 mg N/(g MLVSS·h)) compared to ethanol (1.1 and 0.7 mg N/ (g MLVSS·h)) for both anoxic electron acceptors (nitrate and nitrite).

Growth Mechanism of Single-Walled Carbon Nanotubes on Iron–Copper Catalyst and Chirality Studies by Electron Diffraction

DEFF Research Database (Denmark)

He, Maoshuai; Liu, Bilu; Chernov, Alexander I.

2012-01-01

Chiralities of single-walled carbon nanotubes grown on an atomic layer deposition prepared bimetallic FeCu/MgO catalyst were evaluated quantitatively using nanobeam electron diffraction. The results reveal that the growth yields nearly 90% semiconducting tubes, 45% of which are of the (6,5) type...... by impregnation, showing similar catalytic performance as the atomic layer deposition-prepared catalyst, yielding single-walled carbon nanotubes with a similar narrow chirality distribution....

Influence of Electrical and Electromagnetic Stimulation on Nerve Regeneration in the Transected Mouse Sciatic Nerve : An Electron Microscopic Study

OpenAIRE

Ogata, Akiko; Matsumoto, Tomoko; Matsubara, Takako; Miki, Akinori

2001-01-01

Influence of electrical and electromagnetic stimulation on nerve regeneration was electron microscopically examined in the transected mouse sciatic nerve. Two days after the transection, several thin regenerating axons (daughter axons) were observed between the myelin sheath and basal lamina of Schwann cells in the proximal stump. Growth cones of the daughter axons contained several small round vesicles and mitochondria, and the shaft of them, neurofilaments, neurotubules and profiles of smoo...

Imaging the interphase of carbon fiber composites using transmission electron microscopy: Preparations by focused ion beam, ion beam etching, and ultramicrotomy

Directory of Open Access Journals (Sweden)

Wu Qing

2015-10-01

Full Text Available Three sample preparation techniques, focused ion beam (FIB, ion beam (IB etching, and ultramicrotomy (UM were used in comparison to analyze the interphase of carbon fiber/epoxy composites using transmission electron microscopy. An intact interphase with a relatively uniform thickness was obtained by FIB, and detailed chemical analysis of the interphase was investigated by electron energy loss spectroscopy. It shows that the interphase region is 200 nm wide with an increasing oxygen-to-carbon ratio from 10% to 19% and an almost constant nitrogen-to-carbon ratio of about 3%. However, gallium implantation of FIB tends to hinder fine structure analysis of the interphase. For IB etching, the interphase region is observed with transition morphology from amorphous resin to nano-crystalline carbon fiber, but the uneven sample thickness brings difficulty for quantitative chemical analysis. Moreover, UM tends to cause damage and/or deformation on the interphase. These results are meaningful for in-depth understanding on the interphase characteristic of carbon fiber composites.

Stimulated scattering of electromagnetic waves carrying orbital angular momentum in quantum plasmas.

Science.gov (United States)

Shukla, P K; Eliasson, B; Stenflo, L

2012-07-01

We investigate stimulated scattering instabilities of coherent circularly polarized electromagnetic (CPEM) waves carrying orbital angular momentum (OAM) in dense quantum plasmas with degenerate electrons and nondegenerate ions. For this purpose, we employ the coupled equations for the CPEM wave vector potential and the driven (by the ponderomotive force of the CPEM waves) equations for the electron and ion plasma oscillations. The electrons are significantly affected by the quantum forces (viz., the quantum statistical pressure, the quantum Bohm potential, as well as the electron exchange and electron correlations due to electron spin), which are included in the framework of the quantum hydrodynamical description of the electrons. Furthermore, our investigation of the stimulated Brillouin instability of coherent CPEM waves uses the generalized ion momentum equation that includes strong ion coupling effects. The nonlinear equations for the coupled CPEM and quantum plasma waves are then analyzed to obtain nonlinear dispersion relations which exhibit stimulated Raman, stimulated Brillouin, and modulational instabilities of CPEM waves carrying OAM. The present results are useful for understanding the origin of scattered light off low-frequency density fluctuations in high-energy density plasmas where quantum effects are eminent.

Stability and Electronic Properties of Hydrogenated Zigzag Carbon Nanotube Focused on Stone-Wales Defect

International Nuclear Information System (INIS)

Pan Li-Jun; Zhang Jie; Chen Wei-Guang; Tang Ya-Nan

2015-01-01

We present a first-principles study of the chemisorption of hydrogen on a Stone-Wales (SW) defective carbon nanotube (10,0). The investigated configurations include four configurations covering single defects and double defects. One hydrogen dimer adsorption is energetically favored on bonds shared by carbon heptagon-heptagon for configurations with the defect parallel to the tube axis compared with the carbon pentagon-hexagon sites for ones with a slanted defect. This different behavior is also demonstrated for hydrogen dimer chain adsorption, the favored site for the former ones is through the defect, which is the nearest neighbor site to defect for the latter ones. It is found that the energy band gaps of hydrogenated configurations may be enlarged or decreased by altering the adsorption site or defect position. The semiconductor-to-metal transition may occur for configurations with the defect or defects parallel to the tube axis due to low electronic localization. Our results highlight the interest of the interaction of multi-factor system by providing a detailed bond and position picture of a hydrogenated defective carbon nanotube (10,0). (paper)

Electronic transport in large systems through a QUAMBO-NEGF approach: Application to atomic carbon chains

International Nuclear Information System (INIS)

Fang, X.W.; Zhang, G.P.; Yao, Y.X.; Wang, C.Z.; Ding, Z.J.; Ho, K.M.

2011-01-01

The conductance of single-atom carbon chain (SACC) between two zigzag graphene nanoribbons (GNR) is studied by an efficient scheme utilizing tight-binding (TB) parameters generated via quasi-atomic minimal basis set orbitals (QUAMBOs) and non-equilibrium Green's function (NEGF). Large systems (SACC contains more than 50 atoms) are investigated and the electronic transport properties are found to correlate with SACC's parity. The SACCs provide a stable off or on state in broad energy region (0.1-1 eV) around Fermi energy. The off state is not sensitive to the length of SACC while the corresponding energy region decreases with the increase of the width of GNR. -- Highlights: → Graphene has many superior electronic properties. → First-principles calculation are accurate but limited to system size. → QUAMBOs construct tight-binding parameters with spatial localization, and then use divide-and-conquer method. → SACC (single carbon atom chain): structure and transport show even-odd parity, and long chains are studied.

WO3 nanorods-modified carbon electrode for sustained electron uptake from Shewanella oneidensis MR-1 with suppressed biofilm formation

International Nuclear Information System (INIS)

Zhang, Feng; Yuan, Shi-Jie; Li, Wen-Wei; Chen, Jie-Jie; Ko, Chi-Chiu; Yu, Han-Qing

2015-01-01

Highlights: • WO 3 nanorods-modified carbon paper was used as the anode of MFC. • WO 3 nanorods suppressed biofilm growth on the electrode surface. • Sustained electron transfer from cells to electrode via riboflavin was achieved. • C–WO 3 nanorods enable stable and efficient EET process in long-time operation. - Abstract: Carbon materials are widely used as electrodes for bioelectrochemical systems (BES). However, a thick biofilm tends to grow on the electrode surface during continuous operation, resulting in constrained transport of electrons and nutrients at the cell-electrode interface. In this work, we tackled this problem by adopting a WO 3 -nanorods modified carbon electrode (C–WO 3 nanorods), which completely suppressed the biofilm growth of Shewanella Oneidensis MR-1. Moreover, the C–WO 3 nanorods exhibited high electric conductivity and strong response to riboflavin. These two factors together make it possible for the C–WO 3 nanorods to maintain a sustained, efficient process of electron transfer from the MR-1 planktonic cells. As a consequence, the microbial fuel cells with C–WO 3 nanorods anode showed more stable performance than the pure carbon paper and WO 3 -nanoparticles systems in prolonged operation. This work suggests that WO 3 nanorods have the potential to be used as a robust and biofouling-resistant electrode material for practical bioelectrochemical applications

Electron beam processing of carbon fibre reinforced braided composites beams

International Nuclear Information System (INIS)

Halasz, L.; Zsigmond, B.; Czvikovszky, T.

2002-01-01

Complete text of publication follows. In this paper the possibility of producing a new type carbon fiber reinforced composite is examined by applying braiding, a well-known process of textile technology. The appearance of the new Hungarian carbon fiber with excellent mechanical properties in the market enables the development of newer type carbon fiber reinforced composites in the continuously widening range of engineering applications. Advanced hollow profiles, pipes and other composite products can be manufactured in continuous operation. A new way of composite production of this kind is the manufacturing of reinforcing structure by braiding technology producing a composite with sufficient mechanical properties from this cross directional fabric-like textile structure by impregnation. This manufacturing process can complete the variety of hollow products serving the same purpose as pultrusion or filament winding. This way a profile type framework element with a hollow cross section is manufactured having favorable mechanical properties. Owing to its small mass and high specific strength this product can be applied in dynamically loaded structures e.g. in the automotive industry. For crosslinking of the matrix the method of high-speed electron beam curing has been examined in order to reach continuous operation. The field of use and application of carbon fiber braided structures has a great chance especially in machine engineering and in the automotive industry. The main reason for this is that braiding processes are capable of producing structures having good mechanical properties at a low processing price. The mass of the composite load-bearing structure produced this way is one fifth of the steel product having similar geometry, and its specific mechanical properties are nearly as good as that of the most commonly applied semiproduct and structural component, the welded steel profile

Electronically switchable sham transcranial magnetic stimulation (TMS system.

Directory of Open Access Journals (Sweden)

Fumiko Hoeft

Full Text Available Transcranial magnetic stimulation (TMS is increasingly being used to demonstrate the causal links between brain and behavior in humans. Further, extensive clinical trials are being conducted to investigate the therapeutic role of TMS in disorders such as depression. Because TMS causes strong peripheral effects such as auditory clicks and muscle twitches, experimental artifacts such as subject bias and placebo effect are clear concerns. Several sham TMS methods have been developed, but none of the techniques allows one to intermix real and sham TMS on a trial-by-trial basis in a double-blind manner. We have developed an attachment that allows fast, automated switching between Standard TMS and two types of control TMS (Sham and Reverse without movement of the coil or reconfiguration of the setup. We validate the setup by performing mathematical modeling, search-coil and physiological measurements. To see if the stimulus conditions can be blinded, we conduct perceptual discrimination and sensory perception studies. We verify that the physical properties of the stimulus are appropriate, and that successive stimuli do not contaminate each other. We find that the threshold for motor activation is significantly higher for Reversed than for Standard stimulation, and that Sham stimulation entirely fails to activate muscle potentials. Subjects and experimenters perform poorly at discriminating between Sham and Standard TMS with a figure-of-eight coil, and between Reverse and Standard TMS with a circular coil. Our results raise the possibility of utilizing this technique for a wide range of applications.

Sustained stimulation of soil respiration after 10 years of experimental warming

International Nuclear Information System (INIS)

Reth, S; Graf, W; Reichstein, M; Munch, J C

2009-01-01

A number of forest and grassland studies indicated that stimulation of the soil respiration by soil warming ceases after a couple of years (Luo et al 2001 Nature 413 622-5). Here we present results from a long-term soil warming lysimeter experiment in southern Germany showing sustained stimulation of soil respiration after 10 years. Moreover, both warmed and control treatments exhibited a similar temperature response of soil respiration, indicating that adaptation in terms of temperature sensitivity was absent. Carbon dioxide concentration measurements within the profiles are supporting these findings. The increased soil respiration occurred although vegetation productivity in the warmed treatment was not higher than in the control plots. These findings strongly contrast with current soil carbon modeling concepts, where carbon pools decay according to first-order kinetics, and thus a depletion of labile soil carbon pools leads to an apparent down-regulation of microbial respiration (Knorr et al 2005 Nature 433 298-301). Consequently, the potential for positive climate carbon cycle feedback may be larger than represented in current models of soil carbon turnover.

Large work function difference driven electron transfer from electrides to single-walled carbon nanotubes

KAUST Repository

Menamparambath, Mini Mol; Park, Jong Ho; Yoo, Ho Sung; Patole, Shashikant P.; Yoo, Ji Beom; Kim, Sung Wng; Baik, Seunghyun

2014-01-01

V. Here we investigated charge transfer between two different types of electrides, [Ca2N]+·e- and [Ca 24Al28O64]4+·4e-, and single-walled carbon nanotubes (SWNTs) with a work function of 4.73-5.05 eV. [Ca2N]+·e- with open 2-dimensional electron layers

High electron thermal conductivity of chiral carbon nanotubes

International Nuclear Information System (INIS)

Mensah, S.Y.; Allotey, F.K.A.; Nkrumah, George; Mensah, N.G.

2003-11-01

Solving the Boltzmann kinetic equation with energy dispersion relation obtained in the tight binding approximation, the carrier thermal conductivity κ e of a chiral carbon nanotube (CCNT) was determined. The dependence of κ e on temperature T, chiral geometric angle φ h and overlap integrals Δ z and Δ s were obtained. The results were numerically analysed. Unusually high values of κ e were observed suggesting that ne is nontrivial in the calculation of the thermal conductivity κ of CCNT. More interestingly we noted also that at 104 K and for Δ z and Δ s values of 0.020 eV and 0.0150 eV respectively the κ e value is about 41000 W/mK as reported for a 99.9% pure 12 C crystal. We predict that the electron thermal conductivity of CCNT should exceed 200,000 W/mK at ∼ 80 K. (author)

Investigation of metal/carbon-related materials for fuel cell applications by electronic structure calculations

Energy Technology Data Exchange (ETDEWEB)

Kong, Ki-jeong [Korea Research Institute of Chemical Technology, P.O.Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of)]. E-mail: kong@krict.re.kr; Choi, Youngmin [Korea Research Institute of Chemical Technology, P.O.Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of); Ryu, Beyong-Hwan [Korea Research Institute of Chemical Technology, P.O.Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of); Lee, Jeong-O [Korea Research Institute of Chemical Technology, P.O.Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of); Chang, Hyunju [Korea Research Institute of Chemical Technology, P.O.Box 107, Yuseong, Daejeon 305-600 (Korea, Republic of)

2006-07-15

The potential of carbon-related materials, such as carbon nanotubes (CNTs) and graphite nanofibers (GNFs), supported metal catalysts as an electrode for fuel cell application was investigated using the first-principle electronic structure calculations. The stable binding geometries and energies of metal catalysts are determined on the CNT surface and the GNF edge. The catalyst metal is more tightly bound to the GNF edge than to the CNT surface because of the existence of active dangling bonds of edge carbon atoms. The diffusion barrier of metal atoms on the surface and edge is also obtained. From our calculation results, we have found that high dispersity is achievable for GNF due to high barrier against the diffusion of metal atoms, while CNT appears less suitable. The GNF with a large edge-to-wall ratio is more suitable for the high-performance electrode than perfect crystalline graphite or CNT.

Investigation of metal/carbon-related materials for fuel cell applications by electronic structure calculations

International Nuclear Information System (INIS)

Kong, Ki-jeong; Choi, Youngmin; Ryu, Beyong-Hwan; Lee, Jeong-O; Chang, Hyunju

2006-01-01

The potential of carbon-related materials, such as carbon nanotubes (CNTs) and graphite nanofibers (GNFs), supported metal catalysts as an electrode for fuel cell application was investigated using the first-principle electronic structure calculations. The stable binding geometries and energies of metal catalysts are determined on the CNT surface and the GNF edge. The catalyst metal is more tightly bound to the GNF edge than to the CNT surface because of the existence of active dangling bonds of edge carbon atoms. The diffusion barrier of metal atoms on the surface and edge is also obtained. From our calculation results, we have found that high dispersity is achievable for GNF due to high barrier against the diffusion of metal atoms, while CNT appears less suitable. The GNF with a large edge-to-wall ratio is more suitable for the high-performance electrode than perfect crystalline graphite or CNT

Electron transfer from electronic excited states to sub-vacuum electron traps in amorphous ice

International Nuclear Information System (INIS)

Vichnevetski, E.; Bass, A.D.; Sanche, L.

2000-01-01

We investigate the electron stimulated yield of electronically excited argon atoms (Ar * ) from monolayer quantities of Ar deposited onto thin films of amorphous ice. Two peaks of narrow width ( - electron-exciton complex into exciton states, by the transfer of an electron into a sub-vacuum electron state within the ice film. However, the 10.7 eV feature is shifted to lower energy since electron attachment to Ar occurs within small pores of amorphous ice. In this case, the excess electron is transferred into an electron trap below the conduction band of the ice layer

Direct electron transfer of glucose oxidase promoted by carbon nanotubes is without value in certain mediator-free applications

International Nuclear Information System (INIS)

Wang, Y.; Yao, Y.

2012-01-01

We have investigated the direct electron transfer (DET) promoted by carbon nanotubes (CNTs) on an electrode containing immobilized glucose oxidase (GOx) with the aim to develop a third-generation glucose biosensor and a mediator-free glucose biofuel cell anode. GOx was immobilized via chitosan (CS) on a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs). Cyclic voltammetric revealed that the GOx on the surface of such an electrode is unable to simultaneously demonstrate DET with the electrode and to retain its catalytic activity towards glucose, although the MWCNTs alone can promote electron transfer between GOx and electrode. This is interpreted in terms of two types of GOx on the surface, the distribution and properties of which are quite different. The first type exhibits DET capability that results from the collaboration of MWCNTs and metal impurities, but is unable to catalyze the oxidation of glucose. The second type maintains its glucose-specific catalytic capability in the presence of a mediator, which can be enhanced by MWCNTs, but cannot undergo DET with the electrode. As a result, the MWCNTs are capable of promoting the electron transfer, but this is without value in some mediator-free applications such as in third-generation glucose biosensors and in mediator-free anodes for glucose biofuel cells. (author)

Enhancement of the water flow velocity through carbon nanotubes resulting from the radius dependence of the friction due to electron excitations

Science.gov (United States)

Sokoloff, J. B.

2018-03-01

Secchi et al. [Nature (London) 537, 210 (2016), 10.1038/nature19315] observed a large enhancement of the permeability and slip length in carbon nanotubes when the tube radius is of the order of 15 nm, but not in boron nitride nanotubes. It will be pointed out that none of the parameters that appear in the usual molecular dynamics treatments of water flow in carbon nanotubes have a length scale comparable to 15 nm, which could account for the observed flow velocity enhancement. It will be demonstrated here, however, that if the friction force between the water and the tube walls in carbon nanotubes is dominated by friction due to electron excitations in the tube walls, the enhanced flow can be accounted for by a reduction in the contribution to the friction due to electron excitations in the wall, resulting from the dependence of the electron energy band gap on the tube radius.

The influence of bubbles on the perception carbonation bite.

Directory of Open Access Journals (Sweden)

Paul M Wise

Full Text Available Although many people naively assume that the bite of carbonation is due to tactile stimulation of the oral cavity by bubbles, it has become increasingly clear that carbonation bite comes mainly from formation of carbonic acid in the oral mucosa. In Experiment 1, we asked whether bubbles were in fact required to perceive carbonation bite. Subjects rated oral pungency from several concentrations of carbonated water both at normal atmospheric pressure (at which bubbles could form and at 2.0 atmospheres pressure (at which bubbles did not form. Ratings of carbonation bite under the two pressure conditions were essentially identical, indicating that bubbles are not required for pungency. In Experiment 2, we created controlled streams of air bubbles around the tongue in mildly pungent CO2 solutions to determine how tactile stimulation from bubbles affects carbonation bite. Since innocuous sensations like light touch and cooling often suppress pain, we predicted that bubbles might reduce rated bite. Contrary to prediction, air bubbles flowing around the tongue significantly enhanced rated bite, without inducing perceived bite in blank (un-carbonated solutions. Accordingly, though bubbles are clearly not required for carbonation bite, they may well modulate perceived bite. More generally, the results show that innocuous tactile stimulation can enhance chemogenic pain. Possible physiological mechanisms are discussed.

Luminescence optically stimulated: theory and applications

International Nuclear Information System (INIS)

Rivera M, T.; Azorin N, J.

2002-01-01

The thermally stimulated luminescence (Tl) has occupied an important place in the Solid state physics (FES) by the flexibility of the phenomena, mainly for its applications in the fields of Radiation Physics (FR) and Medical Physics (MF). The reason of this phenomena lies in the fact of the electrons release by the action of heat. Under that same reason, it can be used the action of another stimulant agent for releasing the trapped electrons in the metastable states (EM), this agent is the light which has the same effect that the heat, giving as result the production of light photons at using light in the visible spectra, of different wavelength that the excitation light. This phenomena is called Luminescence optically stimulated (LOE). The LOE has a great impact in the Solid State Physics (FES), dating and now in the use of the phenomena as a dosimetric method, alternate to the Tl, for its use in the ionizing and non-ionizing radiations fields. (Author)

Electronic structures and three-dimensional effects of boron-doped carbon nanotubes

International Nuclear Information System (INIS)

Koretsune, Takashi; Saito, Susumu

2008-01-01

We study boron-doped carbon nanotubes by first-principles methods based on the density functional theory. To discuss the possibility of superconductivity, we calculate the electronic band structure and the density of states (DOS) of boron-doped (10,0) nanotubes by changing the boron density. It is found that the Fermi level density of states D(ε F ) increases upon lowering the boron density. This can be understood in terms of the rigid band picture where the one-dimensional van Hove singularity lies at the edge of the valence band in the DOS of the pristine nanotube. The effect of three-dimensionality is also considered by performing the calculations for bundled (10,0) nanotubes and boron-doped double-walled carbon nanotubes (10,0)/(19,0). From the calculation of the bundled nanotubes, it is found that interwall dispersion is sufficiently large to broaden the peaks of the van Hove singularity in the DOS. Thus, to achieve the high D(ε F ) using the bundle of nanotubes with single chirality, we should take into account the distance from each nanotube. In the case of double-walled carbon nanotubes, we find that the holes introduced to the inner tube by boron doping spread also on the outer tube, while the band structure of each tube remains almost unchanged.

Influence of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in bicarbonate/carbonate buffer solution

Energy Technology Data Exchange (ETDEWEB)

Li, D.G. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Tubular Goods Research Center of CNPC, Xi' an 710065 (China)], E-mail: dangguoli78@yahoo.com.cn; Feng, Y.R.; Bai, Z.Q. [Tubular Goods Research Center of CNPC, Xi' an 710065 (China); Zhu, J.W.; Zheng, M.S. [School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)

2007-11-01

The influences of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in NaHCO{sub 3}/Na{sub 2}CO{sub 3} buffer solution are investigated by capacitance measurement and electrochemical impedance spectroscopy (EIS). The results show that the passive film appears n-type semiconductive character; with increasing the solution temperature, the addition of chromium into carbon steel and increasing the concentration of chloride ions, the slopes of Mott-Schottky plots decrease, which indicates the increment of the defect density in the passive film. EIS results show that the transfer impedance R{sub 1} and the diffusion impedance W decrease with increasing the solution temperature, with the addition of chromium into carbon steel and with increasing the chloride ions concentration. It can be concluded that the corrosion protection effect of passive film on the substrate decreases with increasing the solution temperature, adding chromium into carbon steel and increasing chloride ions concentration.

Recent Experimental Results on Amorphous Carbon Coatings for Electron Cloud Mitigation

CERN Document Server

Yin Vallgren, C; Chiggiato, P; Costa Pinto, P; Neupert, H; Taborelli, M; Rumolo, G; Shaposhnikova, E; Vollenberg, W

2011-01-01

Amorphous carbon (a-C) thin films, produced in different coating configurations by using DC magnetron sputtering, have been investigated in laboratory for low secondary electron yield (SEY) applications. After the coatings had shown a reliable low initial SEY, the a-C thin films have been applied in the CERN Super Proton Synchrotron (SPS) and tested with Large Hadron Collider (LHC) type beams.Currently, we have used a-C thin film coated in so-called liner configuration for the electron cloud monitors. In addition the vacuum chambers of three dipole magnets have been coated and inserted into the machine. After describing the different configurations used for the coatings, results of the tests in the machine and a summary of the analyses after extraction will be presented. Based on comparison between different coating configurations, a new series of coatings has been applied on three further dipole magnet vacuum chambers. They have been installed and will be tested in coming machine development runs.

Stimulated Raman spectroscopy and nanoscopy of molecules using near field photon induced forces without resonant electronic enhancement gain

Energy Technology Data Exchange (ETDEWEB)

Tamma, Venkata Ananth [CaSTL Center, Department of Chemistry, University of California, Irvine, California 92697 (United States); Huang, Fei; Kumar Wickramasinghe, H., E-mail: hkwick@uci.edu [Department of Electrical Engineering and Computer Science, 142 Engineering Tower, University of California, Irvine, California 92697 (United States); Nowak, Derek [Molecular Vista, Inc., 6840 Via Del Oro, San Jose, California 95119 (United States)

2016-06-06

We report on stimulated Raman spectroscopy and nanoscopy of molecules, excited without resonant electronic enhancement gain, and recorded using near field photon induced forces. Photon-induced interaction forces between the sharp metal coated silicon tip of an Atomic Force Microscope (AFM) and a sample resulting from stimulated Raman excitation were detected. We controlled the tip to sample spacing using the higher order flexural eigenmodes of the AFM cantilever, enabling the tip to come very close to the sample. As a result, the detection sensitivity was increased compared with previous work on Raman force microscopy. Raman vibrational spectra of azobenzene thiol and l-phenylalanine were measured and found to agree well with published results. Near-field force detection eliminates the need for far-field optical spectrometer detection. Recorded images show spatial resolution far below the optical diffraction limit. Further optimization and use of ultrafast pulsed lasers could push the detection sensitivity towards the single molecule limit.

Multiscale characterization of pore spaces using multifractals analysis of scanning electronic microscopy images of carbonates

Directory of Open Access Journals (Sweden)

M. S. Jouini

2011-12-01

Full Text Available Pore spaces heterogeneity in carbonates rocks has long been identified as an important factor impacting reservoir productivity. In this paper, we study the heterogeneity of carbonate rocks pore spaces based on the image analysis of scanning electron microscopy (SEM data acquired at various magnifications. Sixty images of twelve carbonate samples from a reservoir in the Middle East were analyzed. First, pore spaces were extracted from SEM images using a segmentation technique based on watershed algorithm. Pores geometries revealed a multifractal behavior at various magnifications from 800x to 12 000x. In addition, the singularity spectrum provided quantitative values that describe the degree of heterogeneity in the carbonates samples. Moreover, for the majority of the analyzed samples, we found low variations (around 5% in the multifractal dimensions for magnifications between 1700x and 12 000x. Finally, these results demonstrate that multifractal analysis could be an appropriate tool for characterizing quantitatively the heterogeneity of carbonate pore spaces geometries. However, our findings show that magnification has an impact on multifractal dimensions, revealing the limit of applicability of multifractal descriptions for these natural structures.

Electron-stimulated desorption of cesium atoms from cesium layers adsorbed on gold-covered tungsten

Energy Technology Data Exchange (ETDEWEB)

Ageev, V N; Kuznetsov, Yu A; Potekhina, N D, E-mail: kuznets@ms.ioffe.r [A F Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021, St Petersburg (Russian Federation)

2010-03-03

The electron-stimulated desorption (ESD) yields and energy distributions (ED) for neutral cesium atoms have been measured from cesium layers adsorbed on a gold-covered tungsten surface as a function of electron energy, gold film thickness, cesium coverage and substrate temperature. The measurements have been carried out using a time-of-flight method and surface ionization detector in the temperature range 160-300 K. A measurable ESD yield for Cs atoms is observed only after deposition of more than one monolayer of gold and cesium on a tungsten surface at a temperature T = 300 K, which is accompanied by the formation of a CsAu semiconductor film covered with a cesium atom monolayer. The Cs atom ESD yield as a function of incident electron energy has a resonant character and consists of two peaks, the appearance of which depends on both electron energy and substrate temperature. The first peak has an appearance threshold at an electron energy of 57 eV and a substrate temperature of 300 K that is due to Au 5p{sub 3/2} core level excitation in the substrate. The second peak appears at an electron energy of 24 eV and a substrate temperature of 160 K. It is associated with a Cs 5s core level excitation in the Cs adsorbed layer. The Au 5p{sub 3/2} level excitation corresponds to a single broad peak in the ED with a maximum at a kinetic energy of 0.45 eV at a substrate temperature T = 300 K, which is split into two peaks with maxima at kinetic energies of 0.36 and 0.45 eV at a substrate temperature of 160 K, associated with different Cs atom ESD channels. The Cs 5s level excitation leads to an ED for Cs atoms with a maximum at a kinetic energy of approx 0.57 eV which exists only at T < 240 K and low Cs concentrations. The mechanisms for all the Cs atom ESD channels are proposed and compared with the Na atom ESD channels in the Na-Au-W system.

Electron transfer dynamics of triphenylamine dyes bound to TiO2 nanoparticles from femtosecond stimulated Raman spectroscopy

KAUST Repository

Hoffman, David P.

2013-04-11

Interfacial electron transfer between sensitizers and semiconducting nanoparticles is a crucial yet poorly understood process. To address this problem, we have used transient absorption (TA) and femtosecond stimulated Raman spectroscopy (FSRS) to investigate the photoexcited dynamics of a series of triphenylamine-coumarin dye/TiO2 conjugates. The TA decay is multiexponential, spanning time scales from 100 fs to 100 ps, while the characteristic transient Raman spectrum of the radical cation decays biexponentially with a dominant ∼3 ps component. To explain these observations, we propose a model in which the decay of the TA is due to hot electrons migrating from surface trap states to the conduction band of TiO 2 while the decay of the Raman signature is due to internal conversion of the dye molecule. Furthermore, the S1 Raman spectrum of TPAC3, a dye wherein a vinyl group separates the triphenylamine and coumarin moieties, is similar to the S1 Raman spectrum of trans-stilbene; we conclude that their S1 potential energy surfaces and reactivity are also similar. This correlation suggests that dyes containing vinyl linkers undergo photoisomerization that competes with electron injection. © 2013 American Chemical Society.

Theory of multichannel magnetic stimulation: toward functional neuromuscular rehabilitation.

Science.gov (United States)

Ruohonen, J; Ravazzani, P; Grandori, F; Ilmoniemi, R J

1999-06-01

Human excitable cells can be stimulated noninvasively with externally applied time-varying electromagnetic fields. The stimulation can be achieved either by directly driving current into the tissue (electrical stimulation) or by means of electro-magnetic induction (magnetic stimulation). While the electrical stimulation of the peripheral neuromuscular system has many beneficial applications, peripheral magnetic stimulation has so far only a few. This paper analyzes theoretically the use of multiple magnetic stimulation coils to better control the excitation and also to eventually mimic electrical stimulation. Multiple coils allow electronic spatial adjustment of the shape and location of the stimulus without moving the coils. The new properties may enable unforeseen uses for peripheral magnetic stimulation, e.g., in rehabilitation of patients with neuromuscular impairment.

Modeling of the shape of infrared stimulated luminescence signals in feldspars

DEFF Research Database (Denmark)

Pagonis, Vasilis; Jain, Mayank; Murray, Andrew S.

2012-01-01

This paper presents a new empirical model describing infrared (IR) stimulation phenomena in feldspars. In the model electrons from the ground state of an electron trap are raised by infrared optical stimulation to the excited state, and subsequently recombine with a nearest-neighbor hole via...... corresponds to a fast rate of recombination processes taking place along the infrared stimulated luminescence (IRSL) curves. The subsequent decay of the simulated IRSL signal is characterized by a much slower recombination rate, which can be described by a power-law type of equation.Several simulations...

Cobalt magnetic nanoparticles embedded in carbon matrix: biofunctional validation

Energy Technology Data Exchange (ETDEWEB)

Krolow, Matheus Z., E-mail: matheuskrolow@ifsul.edu.br [Universidade Federal de Pelotas, Engenharia de Materiais, Centro de Desenvolvimento Tecnologico (Brazil); Monte, Leonardo G.; Remiao, Mariana H.; Hartleben, Claudia P.; Moreira, Angela N.; Dellagostin, Odir A. [Universidade Federal de Pelotas, Nucleo de Biotecnologia, Centro de Desenvolvimento Tecnologico (Brazil); Piva, Evandro [Universidade Federal de Pelotas, Faculdade de Odontologia (Brazil); Conceicao, Fabricio R. [Universidade Federal de Pelotas, Nucleo de Biotecnologia, Centro de Desenvolvimento Tecnologico (Brazil); Carreno, Neftali L. V. [Universidade Federal de Pelotas, Engenharia de Materiais, Centro de Desenvolvimento Tecnologico (Brazil)

2012-09-15

Carbon nanostructures and nanocomposites display versatile allotropic morphologies, physico-chemical properties and have a wide range of applications in mechanics, electronics, biotechnology, structural material, chemical processing, and energy management. In this study we report the synthesis, characterization, and biotechnological application of cobalt magnetic nanoparticles, with diameter approximately 15-40 nm, embedded in carbon structure (Co/C-MN). A single-step chemical process was used in the synthesis of the Co/C-MN. The Co/C-MN has presented superparamagnetic behavior at room temperature an essential property for immunoseparation assays carried out here. To stimulate interactions between proteins and Co/C-MN, this nanocomposite was functionalized with acrylic acid (AA). We have showed the bonding of different proteins onto Co/C-AA surface using immunofluorescence assay. A Co/C-AA coated with monoclonal antibody anti-pathogenic Leptospira spp. was able to capture leptospires, suggesting that it could be useful in immunoseparation assays.

Characterization of nanometer-scale porosity in reservoir carbonate rock by focused ion beam-scanning electron microscopy.

Science.gov (United States)

Bera, Bijoyendra; Gunda, Naga Siva Kumar; Mitra, Sushanta K; Vick, Douglas

2012-02-01

Sedimentary carbonate rocks are one of the principal porous structures in natural reservoirs of hydrocarbons such as crude oil and natural gas. Efficient hydrocarbon recovery requires an understanding of the carbonate pore structure, but the nature of sedimentary carbonate rock formation and the toughness of the material make proper analysis difficult. In this study, a novel preparation method was used on a dolomitic carbonate sample, and selected regions were then serially sectioned and imaged by focused ion beam-scanning electron microscopy. The resulting series of images were used to construct detailed three-dimensional representations of the microscopic pore spaces and analyze them quantitatively. We show for the first time the presence of nanometer-scale pores (50-300 nm) inside the solid dolomite matrix. We also show the degree of connectivity of these pores with micron-scale pores (2-5 μm) that were observed to further link with bulk pores outside the matrix.

Investigation of Basic Mechanisms of Radiation Effects in Carbon-Based Electronic Materials

Science.gov (United States)

2017-06-01

electron volt (eV) 1.602 177 × 10 –19 joule (J) erg 1 × 10 –7 joule (J) kiloton (kt) (TNT equivalent) 4.184 × 10 12 joule (J) British thermal ...graduate, 2 Ph.D. graduates (one that continued for a follow on year as a post doc), and partially supported 1 additional Ph.D. student , 1 additional post...June (2011) 35. E. Comfort et al., “Creation of individual defects at extremely high proton fluences in carbon nanotube p-n diodes”, IEEE Trans. Nucl

Electronic structure of single- and multiple-shell carbon fullerenes

International Nuclear Information System (INIS)

Lin, Y.; Nori, F.

1994-01-01

We study the electronic states of giant single-shell and the recently discovered nested multiple-shell carbon fullerenes within the tight-binding approximation. We use two different approaches, one based on iterations and the other on symmetry, to obtain the π-state energy spectra of large fullerene cages: C 240 , C 540 , C 960 , C 1500 , C 2160 , and C 2940 . Our iteration technique reduces the size of the problem by more than one order of magnitude (factors of ∼12 and 20), while the symmetry-based approach reduces it by a factor of 10. We also find formulas for the highest occupied and lowest unoccupied molecular orbital energies of C 60n 2 fullerenes as a function of n, demonstrating a tendency towards a metallic regime for increasing n. For multiple-shell fullerenes, we analytically obtain the eigenvalues of the intershell interaction

Electronic properties of Cs-intercalated single-walled carbon nanotubes derived from nuclear magnetic resonance

KAUST Repository

Abou-Hamad, E; Goze-Bac, C; Nitze, F; Schmid, M; Aznar, R; Mehring, M; Wå gberg, T

2011-01-01

We report on the electronic properties of Cs-intercalated single-walled carbon nanotubes (SWNTs). A detailed analysis of the 13C and 133Cs nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The 'metallization' of CsxC materials where x=0–0.144 is evidenced from the increased local electronic density of states (DOS) n(EF) at the Fermi level of the SWNTs as determined from spin–lattice relaxation measurements. In particular, there are two distinct electronic phases called α and β and the transition between these occurs around x=0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x<0.05 (α-phase), whereas it reaches a plateau in the range 0.05≤x≤0.143 at high intercalation levels (β-phase). The new β-phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp2) orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(EF), corresponding to different local electronic band structures of the SWNTs.

Electronic properties of Cs-intercalated single-walled carbon nanotubes derived from nuclear magnetic resonance

KAUST Repository

Abou-Hamad, E

2011-05-24

We report on the electronic properties of Cs-intercalated single-walled carbon nanotubes (SWNTs). A detailed analysis of the 13C and 133Cs nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The \\'metallization\\' of CsxC materials where x=0–0.144 is evidenced from the increased local electronic density of states (DOS) n(EF) at the Fermi level of the SWNTs as determined from spin–lattice relaxation measurements. In particular, there are two distinct electronic phases called α and β and the transition between these occurs around x=0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x<0.05 (α-phase), whereas it reaches a plateau in the range 0.05≤x≤0.143 at high intercalation levels (β-phase). The new β-phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp2) orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(EF), corresponding to different local electronic band structures of the SWNTs.

Electron-shading effect on the horizontal aligned growth of carbon nanotubes

International Nuclear Information System (INIS)

Chai Yang; Xiao Zhiyong; Chan, Philip C. H.

2009-01-01

Based on the well-accepted electron-shading theory during plasma processing, we designed microstructures to control the local built-in electric-field on the substrate surface. The distortion magnitude of the electric-field is largest near the sidewalls of the microstructures, creating a horizontal electric-field in this region. We showed that the horizontally aligned carbon nanotubes (CNTs) were grown by making use of this built-in electric-field during the plasma-enhanced chemical vapor deposition process, with a tactical choice of geometries and materials of the microstructures on the substrate. This technique opens up a way to selectively and controllably grow horizontally aligned CNTs on the substrate surface

Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics

International Nuclear Information System (INIS)

Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; De Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel

2017-01-01

Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS. (paper)

Study of nanometric thin pyrolytic carbon films for explosive electron emission cathode in high-voltage planar diode

Energy Technology Data Exchange (ETDEWEB)

Baryshevsky, Vladimir; Belous, Nikolai; Gurinovich, Alexandra; Gurnevich, Evgeny [Research Institute for Nuclear Problems, Belarusian State University, Bobruiskaya Str. 11, Minsk 220030 (Belarus); Kuzhir, Polina, E-mail: polina.kuzhir@gmail.com [Research Institute for Nuclear Problems, Belarusian State University, Bobruiskaya Str. 11, Minsk 220030 (Belarus); National Research Tomsk State University, 36 Lenin Prospekt, Tomsk 634050 (Russian Federation); Maksimenko, Sergey [Research Institute for Nuclear Problems, Belarusian State University, Bobruiskaya Str. 11, Minsk 220030 (Belarus); National Research Tomsk State University, 36 Lenin Prospekt, Tomsk 634050 (Russian Federation); Molchanov, Pavel; Shuba, Mikhail [Research Institute for Nuclear Problems, Belarusian State University, Bobruiskaya Str. 11, Minsk 220030 (Belarus); Roddatis, Vladimir [CIC energiGUNE, Albert Einstein 48, 01510 Minano, Alava (Spain); Institut für Materialphysik of Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Kaplas, Tommi; Svirko, Yuri [Institute of Photonics, University of Eastern Finland, P.O. Box 111, Joensuu FI-80101 (Finland)

2015-04-30

We report on an experimental study of explosive electron emission properties of cathode made by nanometric thin pyrolytic carbon (PyC) films (2–150 nm) deposited on Cu substrate via methane-based chemical vapor deposition. High current density at level of 300 A/cm{sup 2} in 5 · 10{sup −5} Pa vacuum has been observed together with very stable explosive emission from the planar cathode. The Raman spectroscopy investigation proves that the PyC films remain the same after seven shots. According to the optical image analysis of the cathode before and after one and seven shots, we conclude that the most unusual and interesting feature of using the PyC films/Cu cathode for explosive emission is that the PyC layer on the top of the copper target prevents its evaporation and oxidation, which leads to higher emission stability compared to conventional graphitic/Cu cathodes, and therefore results in longer working life. - Highlights: • Explosive electron emission from pyrolytic carbon (PyC) cathode is reported. • We observe high current density, 300 A/cm{sup 2}, and stable emission parameters. • PyC integrity ensures a high application potential for high current electronics.

Investigation of electron heating in laser-plasma interaction

International Nuclear Information System (INIS)

Parvazian, A.; Haji Sharifi, K.

2013-01-01

In this paper, stimulated Raman scattering and electron heating in laser plasma propagating along the plasma fusion is investigated by particle-in cell simulation. Applying an external magnetic field to plasma, production of whistler waves and electron heating associated with whistler waves in the direction perpendicular to external magnetic field was observed in this simulation. The plasma waves with low phase velocities, generated in backward-stimulated Raman scattering and dominating initially in time and space, accelerated the backward electrons by trapping them. Then these electrons promoted to higher energies by the forward-stimulated Raman scattering plasma waves with high phase velocities. This two-stage electron acceleration is more efficient due to the coexistence of these two instabilities.

K{sub 6} carbon: A metallic carbon allotrope in sp{sup 3} bonding networks

Energy Technology Data Exchange (ETDEWEB)

Niu, Chun-Yao; Wang, Xin-Quan; Wang, Jian-Tao, E-mail: wjt@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-02-07

We identify by first-principles calculations a new cubic carbon phase in I4{sub 1}32 (O{sup 8}) symmetry, named K{sub 6} carbon, which has a six atom primitive cell comprising sp{sup 3} hybridized C{sub 3} triangle rings. The structural stability is verified by phonon mode analysis. The calculated elastic constants show that the K{sub 6} carbon is a high ductile material with a density even lower than graphite. Electronic band and density of states calculations reveal that it is a metallic carbon allotrope with a high electronic density of states of ∼0.10 states/eV per atom at the Fermi level. These results broaden our understanding of the structural and electronic properties of carbon allotropes.

Carbon fiber on polyimide ultra-microelectrodes

Science.gov (United States)

Gillis, Winthrop F.; Lissandrello, Charles A.; Shen, Jun; Pearre, Ben W.; Mertiri, Alket; Deku, Felix; Cogan, Stuart; Holinski, Bradley J.; Chew, Daniel J.; White, Alice E.; Otchy, Timothy M.; Gardner, Timothy J.

2018-02-01

Objective. Most preparations for making neural recordings degrade over time and eventually fail due to insertion trauma and reactive tissue response. The magnitudes of these responses are thought to be related to the electrode size (specifically, the cross-sectional area), the relative stiffness of the electrode, and the degree of tissue tolerance for the material. Flexible carbon fiber ultra-microelectrodes have a much smaller cross-section than traditional electrodes and low tissue reactivity, and thus may enable improved longevity of neural recordings in the central and peripheral nervous systems. Only two carbon fiber array designs have been described previously, each with limited channel densities due to limitations of the fabrication processes or interconnect strategies. Here, we describe a method for assembling carbon fiber electrodes on a flexible polyimide substrate that is expected to facilitate the construction of high-density recording and stimulating arrays. Approach. Individual carbon fibers were aligned using an alignment tool that was 3D-printed with sub-micron resolution using direct laser writing. Indium deposition on the carbon fibers, followed by low-temperature microsoldering, provided a robust and reliable method of electrical connection to the polyimide interconnect. Main results. Spontaneous multiunit activity and stimulation-evoked compound responses with SNR  >10 and  >120, respectively, were recorded from a small (125 µm) peripheral nerve. We also improved the typically poor charge injection capacity of small diameter carbon fibers by electrodepositing 100 nm-thick iridium oxide films, making the carbon fiber arrays usable for electrical stimulation as well as recording. Significance. Our innovations in fabrication technique pave the way for further miniaturization of carbon fiber ultra-microelectrode arrays. We believe these advances to be key steps to enable a shift from labor intensive, manual assembly to a more automated

Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis.

Science.gov (United States)

Yue, Kai; Peng, Yan; Peng, Changhui; Yang, Wanqin; Peng, Xin; Wu, Fuzhong

2016-01-27

Elevated nitrogen (N) deposition alters the terrestrial carbon (C) cycle, which is likely to feed back to further climate change. However, how the overall terrestrial ecosystem C pools and fluxes respond to N addition remains unclear. By synthesizing data from multiple terrestrial ecosystems, we quantified the response of C pools and fluxes to experimental N addition using a comprehensive meta-analysis method. Our results showed that N addition significantly stimulated soil total C storage by 5.82% ([2.47%, 9.27%], 95% CI, the same below) and increased the C contents of the above- and below-ground parts of plants by 25.65% [11.07%, 42.12%] and 15.93% [6.80%, 25.85%], respectively. Furthermore, N addition significantly increased aboveground net primary production by 52.38% [40.58%, 65.19%] and litterfall by 14.67% [9.24%, 20.38%] at a global scale. However, the C influx from the plant litter to the soil through litter decomposition and the efflux from the soil due to microbial respiration and soil respiration showed insignificant responses to N addition. Overall, our meta-analysis suggested that N addition will increase soil C storage and plant C in both above- and below-ground parts, indicating that terrestrial ecosystems might act to strengthen as a C sink under increasing N deposition.

Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

International Nuclear Information System (INIS)

Hayashi, Makoto

2003-04-01

A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO 2 ). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO 2 . Finally, author's comments for CO 2 electron collision cross sections are given. (author)

Number distribution of emitted electrons by MeV H+ impact on carbon

Science.gov (United States)

Ogawa, H.; Koyanagi, Y.; Hongo, N.; Ishii, K.; Kaneko, T.

2017-09-01

The statistical distributions of the number of the forward- and backward-emitted secondary electrons (SE's) from a thin carbon foil have been measured in coincidence with foil-transmitted H+ ions of 0.5-3.0 MeV in every 0.5 MeV step. The measured SE energy spectra were fitted by assuming a Pólya distribution for the simultaneous n-SE emission probabilities. For our previous data with a couple of the carbon foils with different thicknesses, a similar analysis has been carried out. As a result, it was found that the measured spectra could be reproduced as well as by an analysis without placing any restriction on the emission probabilities both for the forward and backward SE emission. The obtained b-parameter of the Pólya distribution, which is a measure of the deviation from a Poisson distribution due to the cascade multiplication by high energy internal SE's, increases monotonically with the incident energy of proton beams. On the other hand, a clear foil-thickness dependence is not observed for the b-parameter. A theoretical model which could reproduced the magnitude of the b-parameter for the SE energy spectra obtained with thick Au, Cu and Al targets is found to overestimates our values for thin carbon foils significantly. Another model calculation is found to reproduce our b-values very well.

Pseudo-topotactic conversion of carbon nanotubes to T-carbon nanowires under picosecond laser irradiation in methanol.

Science.gov (United States)

Zhang, Jinying; Wang, Rui; Zhu, Xi; Pan, Aifei; Han, Chenxiao; Li, Xin; Dan Zhao; Ma, Chuansheng; Wang, Wenjun; Su, Haibin; Niu, Chunming

2017-09-25

Pseudo-topotactic conversion of carbon nanotubes into one-dimensional carbon nanowires is a challenging but feasible path to obtain desired diameters and morphologies. Here, a previously predicted but experimentally unobserved carbon allotrope, T-carbon, has been produced from pseudo-topotactic conversion of a multi-walled carbon nanotube suspension in methanol by picosecond pulsed-laser irradiation. The as-grown T-carbon nanowires have the same diameter distribution as pristine carbon nanotubes, and have been characterized by high-resolution transmission electron microscopy, fast Fourier transform, electron energy loss, ultraviolet-visible, and photoluminescence spectroscopies to possess a diamond-like lattice, where each carbon is replaced by a carbon tetrahedron, and a lattice constant of 7.80 Å. The change in entropy from carbon nanotubes to T-carbon reveals the phase transformation to be first order in nature. The computed electronic band structures and projected density of states are in good agreement with the optical absorption and photoluminescence spectra of the T-carbon nanowires.T-carbon is a previously predicted but so far unobserved allotrope of carbon, with a crystal structure similar to diamond, but with each atomic lattice position replaced by a carbon tetrahedron. Here, the authors produce T-carbon nanowires via laser-irradiating a suspension of carbon nanotubes in methanol.

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices.

Science.gov (United States)

Batra, Nitin M; Patole, Shashikant P; Abdelkader, Ahmed; Anjum, Dalaver H; Deepak, Francis L; Costa, Pedro M F J

2015-11-06

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode-interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode-nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices

KAUST Repository

Batra, Nitin M; Patole, Shashikant P.; Abdelkader, Ahmed; Anjum, Dalaver H.; Deepak, Francis L; Da Costa, Pedro M. F. J.

2015-01-01

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode–interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode–nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices

KAUST Repository

Batra, Nitin M

2015-10-09

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode–interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode–nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Growth Termination and Multiple Nucleation of Single-Wall Carbon Nanotubes Evidenced by in Situ Transmission Electron Microscopy

DEFF Research Database (Denmark)

Zhang, Lili; He, Maoshuai; Hansen, Thomas Willum

2017-01-01

and successive growth of additional SWCNTs on Co catalyst particles supported on MgO by means of environmental transmission electron microscopy. Such in situ observations reveal the plethora of solid carbon formations at the local scale while it is happening and thereby elucidate the multitude of configurations...

Four- and eight-membered rings carbon nanotubes: A new class of carbon nanomaterials

Directory of Open Access Journals (Sweden)

Fangfang Li

2018-06-01

Full Text Available A new class of carbon nanomaterials composed of alternating four- and eight-membered rings is studied by density functional theory (DFT, including single-walled carbon nanotubes (SWCNTs double-walled carbon nanotubes (DWCNTs and triple-walled CNTs (TWCNTs. The analysis of geometrical structure shows that carbon atoms’ hybridization in novel carbon tubular clusters (CTCs and the corresponding carbon nanotubes (CNTs are both sp2 hybridization; The thermal properties exhibit the high stability of these new CTCs. The results of energy band and density of state (DOS indicate that the electronic properties of CNTs are independent of their diameter, number of walls and chirality, exhibit obvious metal properties. Keywords: Four- and eight-membered rings, Carbon nanotubes, Stability, Electronic properties

Application of electron energy loss spectroscopy for single wall carbon nanotubes (review)

International Nuclear Information System (INIS)

Mittal, N.; Jain, S.; Mittal, J.

2015-01-01

Electron energy loss spectroscopy (EELS) is among the few techniques that are available for the characterization of modified single wall carbon nanotubes (SWCNTs) having nanometer dimensions (~1-3 nm). CNTs can be modified either by surface functionalization or coating, between bundles of nanotubes by doping, intercalation and fully or partially filling the central core. EELS is an exclusive technique for the identification, composition analysis, and crystallization studies of the chemicals and materials used for the modification of SWCNTs. The present paper serves as a compendium of research work on the application of EELS for the characterization of modified SWCNTs. (authors)

Dose response of commercially available optically stimulated luminescent detector, Al2O3:C for megavoltage photons and electrons.

Science.gov (United States)

Kim, Dong Wook; Chung, Weon Kuu; Shin, Dong Oh; Yoon, Myonggeun; Hwang, Ui-Jung; Rah, Jeong-Eun; Jeong, Hojin; Lee, Sang Yeob; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong

2012-04-01

This study examined the dose response of an optically stimulated luminescence dosemeter (OSLD) to megavoltage photon and electron beams. A nanoDot™ dosemeter was used to measure the dose response of the OSLD. Photons of 6-15 MV and electrons of 9-20 MeV were delivered by a Varian 21iX machine (Varian Medical System, Inc. Milpitas, CA, USA). The energy dependency was dose was linear until 200 cGy. The superficial dose measurements revealed photon irradiation to have an angular dependency. The nanoDot™ dosemeter has potential use as an in vivo dosimetric tool that is independent of the energy, has dose linearity and a rapid response compared with normal in vivo dosimetric tools, such as thermoluminescence detectors. However, the OSLD must be treated very carefully due to the high angular dependency of the photon beam.

Surface and electron emission properties of hydrogen-free diamond-like carbon films investigated by atomic force microscopy

International Nuclear Information System (INIS)

Liu Dongping; Zhang, Sam; Ong, S.-E.; Benstetter, Guenther; Du Hejun

2006-01-01

In this study, we have deposited hydrogen-free diamond-like carbon (DLC) films by using DC magnetron sputtering of graphite target at various r.f. bias voltages. Surface and nanoscale emission properties of these DLC films have been investigated using a combination of atomic force microscopy (AFM)-based nanowear tests and conducting-AFM, by simultaneously measuring the topography and the conductivity of the samples. Nanowear tests show that these DLC films are covered with the thin (1.5-2.0 nm) graphite-like layers at surfaces. Compared to the film bulk structure, the graphite-like surface layers are more conductive. The graphite-like surface layers significantly influence the electron emission properties of these films. Low-energy carbon species can be responsible for the formation of graphite-like surface layers. Nanoscale electron emission measurements have revealed the inhomogeneous emission nature of these films. The low-field emission from these films can be attributed to the existence of sp 2 -configured nanoclusters inside the films

Electron Emitters

National Research Council Canada - National Science Library

Tzeng, Yonhua

2002-01-01

When two carbon-nanotube coated electrodes are placed at a small distance from each other, electron emission from carbon nanotubes allows a DC or AC electrical current to flow between these two electrodes...

Cobalt magnetic nanoparticles embedded in carbon matrix: biofunctional validation

International Nuclear Information System (INIS)

Krolow, Matheus Z.; Monte, Leonardo G.; Remião, Mariana H.; Hartleben, Cláudia P.; Moreira, Ângela N.; Dellagostin, Odir A.; Piva, Evandro; Conceição, Fabricio R.; Carreño, Neftalí L. V.

2012-01-01

Carbon nanostructures and nanocomposites display versatile allotropic morphologies, physico-chemical properties and have a wide range of applications in mechanics, electronics, biotechnology, structural material, chemical processing, and energy management. In this study we report the synthesis, characterization, and biotechnological application of cobalt magnetic nanoparticles, with diameter approximately 15–40 nm, embedded in carbon structure (Co/C-MN). A single-step chemical process was used in the synthesis of the Co/C-MN. The Co/C-MN has presented superparamagnetic behavior at room temperature an essential property for immunoseparation assays carried out here. To stimulate interactions between proteins and Co/C-MN, this nanocomposite was functionalized with acrylic acid (AA). We have showed the bonding of different proteins onto Co/C-AA surface using immunofluorescence assay. A Co/C-AA coated with monoclonal antibody anti-pathogenic Leptospira spp. was able to capture leptospires, suggesting that it could be useful in immunoseparation assays.

Structural, electronic, optical and vibrational properties of nanoscale carbons and nanowires: a colloquial review

International Nuclear Information System (INIS)

Cole, Milton W; Crespi, Vincent H; Dresselhaus, Mildred S; Dresselhaus, Gene; Fischer, John E; Gutierrez, Humberto R; Kojima, K; Wako, K; Mahan, Gerald D; Rao, Apparao M; Sofo, Jorge O; Tachibana, M; Xiong Qihua

2010-01-01

This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C 60 and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature

Structural, electronic, optical and vibrational properties of nanoscale carbons and nanowires: a colloquial review.

Science.gov (United States)

Cole, Milton W; Crespi, Vincent H; Dresselhaus, Mildred S; Dresselhaus, Gene; Fischer, John E; Gutierrez, Humberto R; Kojima, K; Mahan, Gerald D; Rao, Apparao M; Sofo, Jorge O; Tachibana, M; Wako, K; Xiong, Qihua

2010-08-25

This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C(60) and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature

Field Emission from Carbon Nanostructures

Directory of Open Access Journals (Sweden)

Filippo Giubileo

2018-03-01

Full Text Available Field emission electron sources in vacuum electronics are largely considered to achieve faster response, higher efficiency and lower energy consumption in comparison with conventional thermionic emitters. Carbon nanotubes had a leading role in renewing attention to field emission technologies in the early 1990s, due to their exceptional electron emitting properties enabled by their large aspect ratio, high electrical conductivity, and thermal and chemical stability. In the last decade, the search for improved emitters has been extended to several carbon nanostructures, comprising carbon nanotubes, either individual or films, diamond structures, graphitic materials, graphene, etc. Here, we review the main results in the development of carbon-based field emitters.

Large work function difference driven electron transfer from electrides to single-walled carbon nanotubes

KAUST Repository

Menamparambath, Mini Mol

2014-06-23

A difference in work function plays a key role in charge transfer between two materials. Inorganic electrides provide a unique opportunity for electron transfer since interstitial anionic electrons result in a very low work function of 2.4-2.6 eV. Here we investigated charge transfer between two different types of electrides, [Ca2N]+·e- and [Ca 24Al28O64]4+·4e-, and single-walled carbon nanotubes (SWNTs) with a work function of 4.73-5.05 eV. [Ca2N]+·e- with open 2-dimensional electron layers was more effective in donating electrons to SWNTs than closed cage structured [Ca24Al28O64] 4+·4e- due to the higher electron concentration (1.3 × 1022 cm-3) and mobility (∼200 cm 2 V-1 s-1 at RT). A non-covalent conjugation enhanced near-infrared fluorescence of SWNTs as high as 52%. The field emission current density of electride-SWNT-silver paste dramatically increased by a factor of 46000 (14.8 mA cm-2) at 2 V μm-1 (3.5 wt% [Ca2N]+·e-) with a turn-on voltage of 0.85 V μm-1. This journal is © the Partner Organisations 2014.

Evaporation of carbon using electrons of a high density plasma; Evaporacion de carbono usando los electrones de un plasma de alta densidad

Energy Technology Data Exchange (ETDEWEB)

Muhl, S.; Camps, E.; Escobar A, L.; Garcia E, J.L.; Olea, O. [Instituto de Investigaciones en Materiales, UNAM, C.P. 04510 Mexico D.F. (Mexico)

2000-07-01

The high density plasmas are used frequently in the preparation of thin films or surface modification, for example to nitridation. In these processes, are used mainly the ions and the neutrals which compose the plasma. However, the electrons present in the plasma are not used, except in the case of chemical reactions induced by collisions, although the electron bombardment usually get hot the work piece. Through the adequate polarization of a conductor material, it is possible to extract electrons from a high density plasma at low pressure, that could be gotten the evaporation of this material. As result of the interaction between the plasma and the electron flux with the vapor produced, this last will be ionized. In this work, it is reported the use of this novelty arrangement to prepare carbon thin films using a high density argon plasma and a high purity graphite bar as material to evaporate. It has been used substrates outside plasma and immersed in the plasma. Also it has been reported the plasma characteristics (temperature and electron density, energy and ions flux), parameters of the deposit process (deposit rate and ion/neutral rate) as well as the properties of the films obtained (IR absorption spectra and UV/Vis, elemental analysis, hardness and refractive index). (Author)

Trans-membrane electron transfer in red blood cells immobilized in a chitosan film on a glassy carbon electrode

International Nuclear Information System (INIS)

Yu, Chunmei; Wang, Li; Zhu, Zhenkun; Bao, Ning; Gu, Haiying

2014-01-01

We have studied the trans-membrane electron transfer in human red blood cells (RBCs) immobilized in a chitosan film on a glassy carbon electrode (GCE). Electron transfer results from the presence of hemoglobin (Hb) in the RBCs. The electron transfer rate (k s ) of Hb in RBCs is 0.42 s −1 , and <1.13 s −1 for Hb directly immobilized in the chitosan film. Only Hb molecules in RBCs that are closest to the plasma membrane and the surface of the electrode can undergo electron transfer to the electrode. The immobilized RBCs displayed sensitive electrocatalytic response to oxygen and hydrogen peroxide. It is believed that this cellular biosensor is of potential significance in studies on the physiological status of RBCs based on observing their electron transfer on the modified electrode. (author)

In situ high-resolution transmission electron microscopy synthesis observation of nanostructured carbon coated LiFePO 4

Science.gov (United States)

Trudeau, M. L.; Laul, D.; Veillette, R.; Serventi, A. M.; Mauger, A.; Julien, C. M.; Zaghib, K.

In situ high-resolution transmission electron microscopy (HRTEM) studies of the structural transformations that occur during the synthesis of carbon-coated LiFePO 4 (C-LiFePO 4) and heat treatment to elevated temperatures were conducted in two different electron microscopes. Both microscopes have sample holders that are capable of heating up to 1500 °C, with one working under high vacuum and the other capable of operating with the sample surrounded by a low gaseous environment. The C-LiFePO 4 samples were prepared using three different compositions of precursor materials with Fe(0), Fe(II) or Fe(III), a Li-containing salt and a polyethylene- block-poly(ethylene glycol)-50% ethylene oxide or lactose. The in situ TEM studies suggest that low-cost Fe(0) and a low-cost carbon-containing compound such as lactose are very attractive precursors for mass production of C-LiFePO 4, and that 700 °C is the optimum synthesis temperature. At temperatures higher than 800 °C, LiFePO 4 has a tendency to decompose. The same in situ measurements have been made on particles without carbon coat. The results show that the homogeneous deposit of the carbon deposit at 700 °C is the result of the annealing that cures the disorder of the surface layer of bare LiFePO 4. Electrochemical tests supported the conclusion that the C-LiFePO 4 derived from Fe(0) is the most attractive for mass production.

Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

2003-04-01

A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO{sub 2}). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO{sub 2}. Finally, author's comments for CO{sub 2} electron collision cross sections are given. (author)

Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

Energy Technology Data Exchange (ETDEWEB)

Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

2003-04-01

A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO{sub 2}). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO{sub 2}. Finally, author's comments for CO{sub 2} electron collision cross sections are given. (author)

Multi-walled carbon nanotube structural instability with/without metal nanoparticles under electron beam irradiation

Science.gov (United States)

Khan, Imran; Huang, Shengli; Wu, Chenxu

2017-12-01

The structural transformation of multi-walled carbon nanotubes (MWCNT) under electron beam (e-beam) irradiation at room temperature is studied, with respect to a novel passivation effect due to gold nanoparticles (Au NPs). MWCNT structural evolution induced by energetic e-beam irradiation leads to faster shrinkage, as revealed via in situ transmission electron microscopy, while MWCNT surface modification with Au NPs (Au-MWCNT) slows down the shrinkage by impeding the structural evolution process for a prolonged time under the same irradiation conditions. The new relationship between MWCNT and Au-MWCNT shrinking radii and irradiation time illustrates that the MWCNT shrinkage rate is faster than either theoretical predictions or the same process in Au-MWCNTs. As compared with the outer surface energy (positive curvature), the inner surface energy (negative curvature) of the MWCNT contributes more to the athermal evaporation of tube wall atoms, leading to structural instability and shrinkage under e-beam irradiation. Conversely, Au NPs possess only outer surface energy (positive curvature) compared with the MWCNT. Their presence on MWCNT surfaces retards the dynamics of MWCNT structural evolution by slowing down the evaporation process of carbon atoms, thus restricting Au-MWCNT shrinkage. Au NP interaction and growth evolves athermally on MWCNT surfaces, exhibits increase in their size, and indicates the association of this mechanism with the coalescence induced by e-beam activated electronic excitations. Despite their growth, Au NPs show extreme structural stability, and remain crystalline under prolonged irradiation. It is proposed that the surface energy of MWCNTs and Au NPs, together with e-beam activated soft modes or lattice instability effects, predominantly govern all the above varieties of structural evolution.

Electron-stimulated desorption of lithium ions from lithium halide thin films

International Nuclear Information System (INIS)

Markowski, Leszek

2007-01-01

Electron-stimulated desorption of positive lithium ions from thin layers of lithium halides deposited onto Si(1 1 1) are investigated by the time-of-flight technique. The determined values of isotope effect of the lithium ( 6 Li + / 7 Li + ) are 1.60 ± 0.04, 1.466 ± 0.007, 1.282 ± 0.004, 1.36 ± 0.01 and 1.33 ± 0.01 for LiH, LiF, LiCl, LiBr and LiI, respectively. The observed most probable kinetic energies of 7 Li + are 1.0, 1.9, 1.1, 0.9 and 0.9 eV for LiH, LiF, LiCl, LiBr and LiI, respectively, and seem to be independent of the halide component mass. The values of lithium ion emission yield, lithium kinetic energy and lithium isotope effect suggest that the lattice relaxation is only important in the lithium ion desorption process from the LiH system. In view of possible mechanisms and processes involved into lithium ion desorption the obtained results indicate that for LiH, LiCl, LiBr and LiI the ions desorb in a rather classical way. However, for LiF, ion desorption has a more quantum character and the modified wave packet squeezing model has to be taken into account

The reactions of loaded carbon nanotubes, studied by novel electron microscope techniques

International Nuclear Information System (INIS)

Rawcliffe, A.

1999-01-01

A novel electron microscope technique, controlled environment transmission electron microscopy (CETEM), has been used to investigate the reaction of materials loaded within the internal cavities of carbon nanotubes. CETEM allows the introduction of up to 20 mbar of gas around an electron microscope sample, while maintaining a high resolution imaging capability. The microscope is stable, flexible and reliable under these conditions and high resolution images of encapsulated transmission metal oxide reduction have been recorded at 460 deg. C. Recently discovered carbon nanotubes have in theory many applications, many of which will require controlled reliable loading of the internal cavity. However, at present, there is little experimental evidence to confirm theoretical descriptions of the fundamental mechanisms which govern both the extent of loading and the state in which it is found. Similarly, reaction within the cavity and the effect of encapsulation on the nano-scale particle distribution must also be understood, and CETEM proves to be an ideal technique for the study of these processes. Nanotubes have been loaded from aqueous solution with (NH 4 ) 2 IrCI 6 and with molten MoO 3 or K 2 WO 4 /WO 3 . Bulk samples of the first salt are known to decompose spontaneously in air at 200 deg. C, and the bulk oxides are partially reduced at temperature under hydrogen to give potentially useful conducting phases. Comparing the reaction of these materials it is thus possible to: investigate the effect of loading on their reaction; compare the reaction of these materials in- and out-side the tube cavity; and assess the result of violent loading processes on the tubes themselves. Fortuitously, a spontaneous decomposition, a solid-gas reduction and a phase rearrangement were all recorded, allowing mechanistic implications of encapsulation to be considered for each of these reactions. Perhaps surprisingly, the results can be largely interpreted using the reported bulk

Characterization of Carbon Coatings with Low Secondary Electron Yield

CERN Document Server

Yin Vallgren, C; Costa Pinto, P; Kuzucan, A; Neupert, H; Taborelli, M

2011-01-01

Amorphous carbon (a-C) coatings can reliably be produced with a maximum secondary electron yield (SEY) close to 1 at room temperature. Measurements at low temperature (LHe) are in progress. Analysis by X-ray Photoemission Spectroscopy (XPS) shows a correlation between the lineshape of C1s spectrum in XPS and the maximum SEY of the investigated samples. The initial level of oxygen on the surface of the various samples does not seem to be related to the initial maximum SEY value. However, the increase of the SEY with air exposure time on each individual sample is related to the amount of oxygen containing adsorbates. Storage in different environments has been investigated (static vacuum, aluminium foil, dry nitrogen and desiccators), and shows significant differences in the “aging” behaviour. Aging is very moderate when storing samples wrapped in aluminium foil in air. Samples which have undergone aging due to inappropriate storage can be recovered nearly to the initial value of their SEY by surface treatme...

Enhancement of heterogeneous electron transfer dynamics tuning single-walled carbon nanotube forest height and density

International Nuclear Information System (INIS)

Lamberti, Francesco; Ferraro, Davide; Giomo, Monica; Elvassore, Nicola

2013-01-01

Electrochemical sensors are growing in number and importance. Surface modifications could enhance charge transfer properties occurring at the interfaces and carbon nanoassemblies is one of the most used strategy to improve sensitivity to measurements. However, well defined protocols of surface modification are needed in order to fabricate electrochemically effective nanostructured sensors. Therefore, we aim at investigating the electrochemical properties of single-walled carbon nanotube (SWCNT) forests as a function of height and nanotube surface density. Height of the forests is accurately controlled tuning the oxidation temperatures in the range of 293–313 K of SWCNTs. The surface density of carbon nanotubes was adjusted developing cysteamine/2-mercaptoethanol (CYS/ME) self-assembled monolayers (SAMs) on gold surfaces at different ratios (1:0, 1:3, 1:10, 1:100, 0:1). Apparent electron transfer rate was analyzed with electrochemical impedance spectroscopy (EIS) and experimental data show that transfer rate constant, k app , increases from 1 × 10 −4 cm/s to 6 × 10 −4 cm/s rising oxidation temperatures (i.e. lowering forest height); therefore forests with reduced height show higher electron transfer rate without significant difference in electrodic reversibility. On the other hand, tuning SWCNT surface density, forests obtained with no ME show optimal Δ peak value of 0.087 ± 0.015 V and highest k app value of 9.15 × 10 −3 cm/s. Surprisingly, electrochemical surface area analysis shows that samples with lower amount of cysteamine have an active surface area three times bigger than samples with 1:3 CYS/ME ratio. Low electrochemical efficiency associated with high active surface may be related to unwanted SWCNT bundles adsorbed on the surface for 1:10 and 1:100 CYS/ME ratio samples as confirmed by AFM morphological characterization. Further investigation shows that a transition from a semi-infinite planar diffusion mechanism to a radial diffusion one takes

Radiation dosimetry by optically stimulated phosphorescence of CaF2:Mn

International Nuclear Information System (INIS)

Bernhardt, R.

1974-01-01

In addition to the light emission which occurs in TL, trapped electrons in CaF 2 :Mn can also be released by stimulation with visible and UV light. The measurement of stimulated light emission is disturbed by illumination. But there is an optically-stimulated phosphorescence, which permits to separate measurement of stimulated light emission and illumination. A theory is given. During illumination a part of the released electrons are captured by flat traps, which are emptied at room temperature. A dose dependent signal can be measured at a defined time after the stimulating pulse of visible light. Dosimeters (CaF 2 :Mn teflon disks) were illuminated by the light of a tungsten lamp. The dose response curve was found to be linear from 1 to 10 5 rads. The response curve obtained for optical stimulation was similar to the TL-response curve. Fading of the optically-stimulated signal was higher than TL-fading. Repeated readings of a single sample are possible. The number of readings is dependent on illumination conditions. Accuracy of sample to sample was about 3.5% (standard deviation). There are two background signals. (1) Post-irradiation phosphorescence occurs. Flat traps are also filled after 60 Co gamma excitation. The measurement of the signal is possible after decay of post-irradiation phosphorescence. (2) There is an optically-excited phosphorescence, which also occurs if all trapped electrons are released. The lower limit of dose measurements is given by deviations of optically-excited emission and the dark-current of the photomultiplier tube. (author)

Multiplicity of secondary electrons emitted by carbon thin targets by impact of H0, H2+ and H3+ projectiles at MeV energies

International Nuclear Information System (INIS)

Vidovic, Zvonimir

1997-01-01

This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H 0 , H 2 + and H 3 + projectiles in the 0.25 - 2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. Phenomenological and theoretical descriptions as well as a summary of the main theoretical models are the subjects of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of the thin carbon foils crossed by an energetic projectile is described in the chapter two. In this chapter there are also presented the method and the algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H 0 atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H 2 + and H 3 + polyatomic ions. The results are interpreted in terms of collective effects in the interactions of the ions with solids. The role of the proximity of the protons, molecular ions fragments, upon the amplitude of these collected effects is evidenced from the study of the statistics of forward emission. The experiments allowed us to shed light on various aspects of atom and polyatomic ion interactions with solid surfaces. (author)

Secondary electron emission of thin carbon foils under the impact of hydrogen atoms, ions and molecular ions, under energies within the MeV range

International Nuclear Information System (INIS)

Vidovic, Z.

1997-06-01

This work focuses on the study of the emission statistics of secondary electrons from thin carbon foils bombarded with H 0 , H 2 + and H 3 + projectiles in the 0.25-2.2 MeV energy range. The phenomenon of secondary electron emission from solids under the impact of swift ions is mainly due to inelastic interactions with target electrons. The phenomenological and theoretical descriptions, as well as a summary of the main theoretical models are the subject of the first chapter. The experimental set-up used to measure event by event the electron emission of the two faces of a thin carbon foil traversed by an energetic projectile is described in the chapter two. In this chapter are also presented the method and algorithms used to process experimental spectra in order to obtain the statistical distribution of the emitted electrons. Chapter three presents the measurements of secondary electron emission induced by H atoms passing through thin carbon foils. The secondary electron yields are studied in correlation with the emergent projectile charge state. We show the peculiar role of the projectile electron, whether it remains or not bound to the incident proton. The fourth chapter is dedicated to the secondary electron emission induced by H 2 + and H 3 + polyatomic ions. The results are interpreted in terms of collective effects in the interactions of these ions with solids. The role of the proximity of the protons, molecular ion fragments, upon the amplitude of these collective effects is evidenced from the study of the statistics of forward emission. These experiences allowed us to shed light on various aspects of atom and polyatomic ion inter-actions with solid surfaces. (author)

The structural and electronic properties of monovalent sidewall functionalized double-walled carbon nanotubes

International Nuclear Information System (INIS)

Jalili, Seifollah; Jamali, Maryam

2012-01-01

Highlights: ► (6,0)-(13,0) DWCNT, built from (6,0) and (13,0) SWCNTs, is a metallic nanotubes. ► NH 2 /(6,0)-(13,0) and COOH/(6,0)-(13,0) is semimetal and semiconductor, respectively. ► In NH 2 /(6,0)-(13,0) electrons transferred mainly from inner tube to NH 2 group. - Abstract: The structural and electronic properties of (6,0)-(13,0) double-walled carbon nanotubes (DWCNTs) and monovalent sidewall functionalized DWCNTs with –NH 2 and –COOH groups were studied using density functional theory. The results show that pure (6,0)-(13,0) DWCNTs are metallic. However, by functionalizing a DWCNT, local distortions are induced in the outer tube sidewall along the radial direction. The resulting structures, NH 2 /(6,0)-(13,0) and COOH/(6,0)-(13,0) DWCNTs, exhibit significant structural changes, and are semimetal with no energy gap and semiconducting with a small energy gap, respectively. In NH 2 /(6,0)-(13,0) DWCNTs, new electronic states are created and distributed on the outer wall and NH 2 group by electron transfer from the inner tube to the NH 2 group. In COOH/(6,0)-(13,0) DWCNTs, new states are created and distributed on the inner wall, but there is insignificant charge transfer between the inner tube and the COOH group. These results confirm that local atomic structural distortion on DWCNTs caused by sidewall functionalization can modify the electronic structures of DWCNTs.

On stimulated scattering of laser light in inertial fusion energy targets

International Nuclear Information System (INIS)

Nikolic, Lj; Skoric, M.M.; Ishiguro, S.; Sato, T.

2002-11-01

Propagation of a laser light through regions of an underdense plasma is an active research topic in laser fusion. In particular, a large effort has been invested in studies of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) which can reflect laser energy and produce energetic particles to preheat a fusion energy target. Experiments, theory and simulations agree on a complex interplay between various laser-plasma instabilities. By particle-in-cell simulations of an underdense electron-plasma, we have found, apart from the standard SRS, a strong backscattering near the electron plasma frequency at densities beyond the quarter critical. This novel instability, recognized in recent experiments as stimulated laser scattering on a trapped electron-acoustic mode (SEAS), is absent from a classical theory of laser-parametric instabilities. A parametric excitation of SEAS instability, is explained by a three-wave resonant decay of the incident laser light into a standing backscattered wave and a slow trapped electron acoustic wave (ω p ). Large SEAS pulsations, eventually suppressed by relativistic heating of electrons, are observed in our simulations. This phenomenon seems relevant to future hohlraum target and fast ignition experiments. (author)

Electron injection mechanisms of green organic light-emitting devices fabricated utilizing a double electron injection layer consisting of cesium carbonate and fullerene

International Nuclear Information System (INIS)

Yang, J.S.; Choo, D.C.; Kim, T.W.; Jin, Y.Y.; Seo, J.H.; Kim, Y.K.

2010-01-01

Electron injection mechanisms of the luminance efficiency of green organic light-emitting devices (OLEDs) fabricated utilizing a cesium carbonate (Cs 2 CO 3 )/fullerene (C 60 ) heterostructure acting as an electron injection layer (EIL) were investigated. Current density-voltage and luminance-voltage measurements showed that the current densities and the luminances of the OLEDs with a Cs 2 CO 3 or Cs 2 CO 3 /C 60 EIL were higher than that of the OLEDs with a Liq EIL. The luminance efficiency of the OLEDs with a Cs 2 CO 3 EIL was almost three times higher than that of the OLEDs with a Liq EIL. Because the electron injection efficiency of the Cs 2 CO 3 layer in OLEDs was different from that of the C 60 layer, the luminance efficiency of the OLEDs with a double EIL consisting of a Cs 2 CO 3 layer and a C 60 layer was smaller than that of the OLEDs with a Cs 2 CO 3 EIL. The electron injection mechanisms of OLEDs with a Cs 2 CO 3 and C 60 double EIL are described on the basis of the experimental results.

Synthesis and Characterization Carbon Nanotubes Doped Carbon Aerogels

Science.gov (United States)

Xu, Yuelong; Yan, Meifang; Liu, Zhenfa

2017-12-01

Polycondensation of phloroglucinol, resorcinol and formaldehyde with carbon nanotube (CNT) as the additives, using sodium carbonate as the catalyst, leads to the formation of CNT - doped carbon aerogels. The structure of carbon aerogels (CAs) with carbon nanotubes (CNTs) were characterized by X-ray diffraction and scanning electron microscopy. The specific surface area, pore size distribution and pore volume were measured by surface area analyzer. The results show that when the optimum doping dosage is 5%, the specific surface area of CNT - doped carbon aerogel is up to 665 m2 g-1 and exhibit plentiful mesoporous.

Influence of Carbon Sources and Electron Shuttles on Ferric Iron Reduction by Cellulomonas sp. Strain ES6

Energy Technology Data Exchange (ETDEWEB)

Erin K. Field; Robin Gerlach; Sridhar Viamajala; Laura K. Jennings; Alfred B. Cunningham; Brent M. Peyton; William A. Apel

2011-09-01

The reduction of hexavalent chromium, Cr(VI), to trivalent chromium, Cr(III), can be an important aspect of remediation processes at Department of Energy (DOE) and other contaminated sites. Cellulomonas species are found at several Cr(VI) contaminated and uncontaminated locations at the DOE site in Hanford, Washington. Members of this genus have demonstrated the ability to effectively reduce Cr(VI) to Cr(III) fermentatively and therefore play a potential role in hexavalent chromium remediation at this site. Batch studies were conducted with Cellulomonas sp. strain ES6 to assess the influence of various carbon sources, iron minerals, and electron shuttling compounds on Cr(VI) reduction. These chemical species are likely to be present in these terrestrial environments during in situ bioremediation. Results indicated that there were a number of interactions between these compounds that influenced Cr(VI) reduction rates. The type of carbon source as well as the type of electron shuttle present influenced Cr(VI) reduction rates. When an electron shuttle, such as anthraquinone-2,6-disulfonate (AQDS), was present in the system, reduction rates increased significantly. Biologically reduced AQDS (AHDS) reduced Cr(VI) almost instantaneously. The presence of iron minerals and their concentrations did not significantly influence Cr(VI) reduction rates. However, strain ES6 or AQDS could directly reduce surface-associated Fe(III) to Fe(II) which was capable of reducing Cr(VI) at a near instantaneous rate. These results suggest the rate limiting step in these systems is the transfer of electrons from strain ES6 to the intermediate or terminal electron acceptor whether that is Cr(VI), Fe(III), or AQDS.

Carbon foam/hydroxyapatite coating for carbon/carbon composites: Microstructure and biocompatibility

Energy Technology Data Exchange (ETDEWEB)

Zhang, Leilei, E-mail: zhangleilei1121@aliyun.com; Li, Hejun; Li, Kezhi; Zhang, Shouyang; Lu, Jinhua; Li, Wei; Cao, Sheng; Wang, Bin

2013-12-01

To improve the surface biocompatibility of carbon/carbon composites, a carbon foam/hydroxyapatite coating was applied using a combination method of slurry procedure and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The biocompatibility of the carbon foam/hydroxyapatite coating was investigated by osteoblast-like MG63 cell culture tests. The results showed that the carbon foam could provide a large number of pores on the surface of carbon/carbon composites. The hydroxyapatite crystals could infiltrate into the pores and form the carbon foam/hydroxyapatite coating. The coating covered the carbon/carbon composites fully and uniformly with slice morphology. The cell response tests showed that the MG63 cells on carbon foam/hydroxyapatite coating had a better cell adhesion and cell proliferation than those on uncoated carbon/carbon composites. The carbon foam/hydroxyapatite coatings were cytocompatible and were beneficial to improve the biocompatibility. The approach presented here may be exploited for fabrication of carbon/carbon composite implant surfaces.

Carbon foam/hydroxyapatite coating for carbon/carbon composites: Microstructure and biocompatibility

International Nuclear Information System (INIS)

Zhang, Leilei; Li, Hejun; Li, Kezhi; Zhang, Shouyang; Lu, Jinhua; Li, Wei; Cao, Sheng; Wang, Bin

2013-01-01

To improve the surface biocompatibility of carbon/carbon composites, a carbon foam/hydroxyapatite coating was applied using a combination method of slurry procedure and ultrasound-assisted electrochemical deposition procedure. The morphology, microstructure and chemical composition of the coating were investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and X-ray diffraction. The biocompatibility of the carbon foam/hydroxyapatite coating was investigated by osteoblast-like MG63 cell culture tests. The results showed that the carbon foam could provide a large number of pores on the surface of carbon/carbon composites. The hydroxyapatite crystals could infiltrate into the pores and form the carbon foam/hydroxyapatite coating. The coating covered the carbon/carbon composites fully and uniformly with slice morphology. The cell response tests showed that the MG63 cells on carbon foam/hydroxyapatite coating had a better cell adhesion and cell proliferation than those on uncoated carbon/carbon composites. The carbon foam/hydroxyapatite coatings were cytocompatible and were beneficial to improve the biocompatibility. The approach presented here may be exploited for fabrication of carbon/carbon composite implant surfaces.

Structural transformations of carbon chains inside nanotubes

International Nuclear Information System (INIS)

Warner, Jamie H.; Ruemmeli, Mark H.; Bachmatiuk, Alicja; Buechner, Bernd

2010-01-01

In situ aberration-corrected high-resolution transmission electron microscopy is used to examine the structural transformations of carbon chains that occur in the interior region of carbon nanotubes. We find electron-beam irradiation leads to the formation of two-dimensional carbon structures that are freely mobile inside the nanotube. The inner diameter of the nanotube influences the structural transformations of the carbon chains. As the diameter of the nanotube increases, electron-beam irradiation leads to curling of the chains and eventually the formation of closed looped structures. The closed looped structures evolve into spherical fullerenelike structures that exhibit translational motion inside the nanotubes and also coalesce to form larger nanotube structures. These results demonstrate the use of carbon nanotubes as test tubes for growing small carbon nanotubes within the interior by using only electron-beam irradiation at 80 kV.

Backward and forward electron emission induced by helium projectiles incident on thin carbon foils: Influence of charge changing processes

Energy Technology Data Exchange (ETDEWEB)

Pauly, N. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium)]. E-mail: nipauly@ulb.ac.be; Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium); Roesler, M. [Karl-Pokern-Str. 12, D-12587 Berlin (Germany)

2007-03-15

The backward and forward electron emission yields {gamma} {sub B} and {gamma} {sub F} have been calculated by Monte Carlo simulations for helium (He{sup ++}, He{sup +} or He{sup 0}) ions incident on thin amorphous carbon foils with energies around the electronic stopping power maximum (0.2-2 MeV). Besides the direct excitation of target electrons by the incident projectile, we have taken into account the different charge changing processes (He{sup ++} {r_reversible} He{sup +} {r_reversible} He{sup 0}) undergone by the helium ion in the target. We discuss in particular the connection between the electron emission yield {gamma} and the electronic stopping power (dE/dx){sub e}. We compare our results with previously published experimental results.

Collisions of carbon and oxygen ions with electrons, H, H2 and He: Volume 5

International Nuclear Information System (INIS)

Phaneuf, R.A.; Janev, R.K.; Pindzola, M.S.

1987-02-01

This report provides a handbook for fusion research of recommended cross-section and rate-coefficient data for collisions of carbon and oxygen ions with electrons, hydrogen atoms and molecules, and helium atoms. Published experimental and theoretical data have been collected and evaluated, and recommended data are presented in tabular, graphical, and parametrized form. Processes considered include exciation, ionization, and charge exchange at collision energies appropriate to applications in fusion-energy research

New Insights on Subsurface Imaging of Carbon Nanotubes in Polymer Composites via Scanning Electron Microscopy

Science.gov (United States)

Zhao, Minhua; Ming, Bin; Kim, Jae-Woo; Gibbons, Luke J.; Gu, Xiaohong; Nguyen, Tinh; Park, Cheol; Lillehei, Peter T.; Villarrubia, J. S.; Vladar, Andras E.;

Multiwall carbon nanotubes modulate paraquat toxicity in Arabidopsis thaliana.

Science.gov (United States)

Fan, Xiaoji; Xu, Jiahui; Lavoie, Michel; Peijnenburg, W J G M; Zhu, Youchao; Lu, Tao; Fu, Zhengwei; Zhu, Tingheng; Qian, Haifeng

2018-02-01

Carbon nanotubes can be either toxic or beneficial to plant growth and can also modulate toxicity of organic contaminants through surface sorption. The complex interacting toxic effects of carbon nanotubes and organic contaminants in plants have received little attention in the literature to date. In this study, the toxicity of multiwall carbon nanotubes (MWCNT, 50 mg/L) and paraquat (MV, 0.82 mg/L), separately or in combination, were evaluated at the physiological and the proteomic level in Arabidopsis thaliana for 7-14 days. The results revealed that the exposure to MWCNT had no inhibitory effect on the growth of shoots and leaves. Rather, MWCNT stimulated the relative electron transport rate and the effective photochemical quantum yield of PSII value as compared to the control by around 12% and lateral root production up to nearly 4-fold as compared to the control. The protective effect of MWCNT on MV toxicity on the root surface area could be quantitatively explained by the extent of MV adsorption on MWCNT and was related to stimulation of photosynthesis, antioxidant protection and number and area of lateral roots which in turn helped nutrient assimilation. The influence of MWCNT and MV on photosynthesis and oxidative stress at the physiological level was consistent with the proteomics analysis, with various over-expressed photosynthesis-related proteins (by more than 2 folds) and various under-expressed oxidative stress related proteins (by about 2-3 folds). This study brings new insights into the interactive effects of two xenobiotics (MWCNT and MV) on the physiology of a model plant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural, elastic and electronic Properties of isotropic cubic crystals of carbon and silicon nanotubes : Density functional based tight binding calculations.

Directory of Open Access Journals (Sweden)

Alexander L. Ivanovskii

2008-01-01

Full Text Available Atomic models of cubic crystals (CC of carbon and graphene-like Si nanotubes are offered and their structural, cohesive, elastic and electronic properties are predicted by means of the DFTB method. Our main findings are that the isotropic crystals of carbon nanotubes adopt a very high elastic modulus B and low compressibility β, namely B = 650 GPa, β = 0.0015 1/GPa. In addition, these crystals preserve the initial conductivity type of their “building blocks”, i.e. isolated carbon and Si nanotubes. This feature may be important for design of materials with the selected conductivity type.

Electron-stimulated desorption from condensed branched alkanes

International Nuclear Information System (INIS)

Kelber, J.A.; Knotek, M.L.

1982-01-01

Desorption of H + , CH 3+ , H 2+ , and D + have been measured as a function of electron excitation energy for solid neopentane, tetramethylsilane and two deuterated isomers of isobutane. The evidence shows that C-C (or Si-C) and C-H bonds are broken by electronic excitations localized on methyl groups, in contrast to CH 3+ production in gas-phase neopentane, and that these excitations are the final states of decay processes initiated by creation of a hole in the C2s level, or, in tetramethylsilane, the C2s/Si3s level. This is in accord with other evidence which shows that localized multi-valence hole states result in C-H, C-C, Si-C and Si-H dissociation, and that such states may be excited either directly or by shakeup, by decay from a C2s hole, or by decay for a C1s core hole. It is apparent then, that dissociation and desorption of ions from covalent materials is a multi (electron) hole mechanism, and that the means of localizing the excitation energy in such systems involves multi-hole correlation

Stimulated Thomson scattering

International Nuclear Information System (INIS)

Spencer, R.L.

1979-03-01

The theory of stimulated Thomson scattering is investigated both quantum mechanically and classically. Two monochromatic electromagnetic waves of like polarization travelling in opposite directions are allowed to interact for a time tau with the electrons in a collisionless plasma. The electromagnetic waves have frequencies well above the plasma frequency, and their difference frequency is allowed to range upward from the plasma frequency. With the difference frequency well above the plasma frequency, the rate at which energy is transferred from one wave to the other is calculated quantum mechanically, classically from a fluid theory, and classically from an independent electron theory. The rate is calculated in both the homogeneously broadened limit, and in the inhomogeneously broadened limit

A Microfabricated Transduction Coil for Inductive Deep Brain Stimulation