bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nano-Particulate of Aluminum Nitride Prepared by Pulsed Wire Discharge
Authors: Kinemuchi Yoshiaki , Sangurai Channarong , Suzuki Tsuneo , Suematsu Hisayuki , Jiang Weihua , Yatsui Kiyoshi 
Published: April 2011

AbstractNanoparticulates of aluminum nitride (AlN) have been synthesized by novel dry process, namely pulsed wire discharge where aluminum wire is exploded by an intense pulsed current (10-20 kA at the peak, half cycle of 10 μs) in NH3/N2 gas. The average size of the nanoparticulates was found to be 28 nm. Furthermore, narrow particle distribution of the particulates was observed, where geometric standard deviation was 1.29. Increasing charging energy enhances the nitridation of aluminum. The maximum content of AlN in synthesized particulates was ∼95 %. The sintered body with 80 % of density has been obtained by sintering at 1, 600°C for one hour.
A Facile Wet Synthesis of Nanoparticles of Litharge, the Tetragonal Form of PbO
Authors: Wilkinson Tommy J. , Perry Dale L. , Spiller Erik , Berdahl Paul , Derenzo Stephen E. , Weber Marvin J. 
Published: April 2011

AbstractThe red, tetragonal form of lead oxide, α-PbO, litharge, has been synthesized in the nanoparticle range using a rapid, one-step reaction sequence using water as the reaction medium. The product was characterized by powder x-ray diffraction and scanning electron microscopy. With time at room temperature, the original material slowly changed in color intensity, indicating its alteration to β-PbO, massicot. Grinding the aged material converted it back to the original litharge form. The role of impurities in the experimental synthesis of the material and microstructural variations in the final product are discussed, along with the PbO-phase compositions of commercial products.
Fabrication and Properties of Self-Assembled Nanosized Magnetic Particles
Authors: Salazar-Alvarez G. , Mikhailova M. , Toprak M. , Zhang Y. , Muhammed M. 
Published: April 2011

AbstractThe synthesis and characterisation of gold-coated cobalt nanoparticles, as well as their chemically- and magnetically-induced self-organisation have been studied. Metallic core-shell nanoparticles were prepared using two different experimental techniques: bulk reductive precipitation, with average particles size ∼15 nm, and microemulsion confining method, with average particle size of ∼6 nm. The self-assembly of prepared nanoparticles on flat substrates was achieved by derivatising the substrate and particle surfaces with bifunctional organic molecules that attaches to both particles and substrates.Examination of the self-assembled systems was carried out by a number of characterisation techniques including transmission electron microscopy (TEM), UV-visible spectrophotometry (UV-VIS), and atomic force microscopy (AFM).
XPS and Magnetization Measurements Study of CrMn Nanoparticles
Authors: Abdul-Razzaq Wathiq , Lee Unchul 
Published: April 2011

AbstractCr1-xMnx (x < 6.3 %) alloy in the bulk form is an interesting complex system that behaves in many but not all respects like a spin-glass system. In this study, 14 nm-size CrMn nanoparticles with 5% Mn, were synthesized by ball milling of Cr and Mn particles in Ar atmosphere. After 50 hours of milling, the x-ray diffraction pattern indicated alloying of the two metals Cr and Mn. However XPS data indicated the formation of MnO2 and Cr2O3oxides on the surface of the chromium core in the nanoparticle. These oxides on the surface, like the Cr core, are antiferromagnets. Magnetization (M) measurement at 200 G as a function of temperature (T), after zero-field-cooling, showed that M increased as T increased from 5 K all the way to 330 K, beyond the Neel temperatures of the Cr and the oxides. Even though the magnetization value is in the range of a typical antiferromagnet at all temperatures from 5 to 330 K, the shape of M versus T curve is neither that of an antiferromagnet nor of a spin-glass. It appears that the behavior of the magnetization curve is due to the frustration of the spins by weak fields associated with spin-density-wave and by the existence of the oxides. This frustration should be different from the frustration of the spins due to the ferromagnetic-antiferromagnetic competition in spin-glass systems.
Preparation and Magnetic Properties of Fe Nanoparticles by Chemical Vapor Condensation Process
Authors: Choi C. J. , Kim B. K. , Dong X. L. 
Published: April 2011

AbstractNano-sized Fe particles were synthesized by Chemical Vapor Condensation (CVC) Process using the precursor of iron carbonyl (Fe(CO)5) as the source. We investigated the microstructures, magnetic properties of the Fe nanoparticles and their oxidation behavior during annealing systematically by means of HRTEM, DTA-TG, Mössbauer spectroscopy. The prepared particle was nearly spherical shape and core-shell type structure. The magnetic states of Fe nanoparticles changed from superparamagnetism to ferromagnetism with the particle size and microstructure. Oxidation heat treatment leads to the successive appearance of oxide phases.
Thermoelectric Study of Hydrogen Storage in Carbon Nanotubes
Authors: Sumanasekera G. U. , Adu C. K. W. , Pradhan B. K. , Chen G. , Romero H. E. , Eklund P. C. 
Published: April 2011

AbstractIn situ resistivity and thermoelectric power (S) have been used to study the nature of the adsorption of hydrogen in bundles of single-walled carbon nanotubes for H2 pressure P <1 atm and temperatures 77 K<T<500 K. Isothermal plots of S vs. Δρ/ρ0 are found to exhibit linear behavior as a function of gas coverage, consistent with a physisorption process. Studies of S, ρ at T = 500 K as a function of pressure exhibit a plateau at a pressure P~40 Torr, the same pressure where the H % measurements suggest the highest binding energy sites are being saturated. The effects of H2 exposure at 500 K on the thermoelectric transport properties are fully reversible.
Nanoengineering of Carbon Nanotubes and the Status of its Applications
Authors: Nakayama Yoshikazu , Akita Seiji 
Published: April 2011

AbstractWe have developed a well-controlled method for manipulating carbon nanotubes. The first crucial process involved is to prepare a nanotube array, named nanotube cartridge. We have found the ac electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge. The nanotubes used were multiwalled and prepared by an arc discharge with a relatively high gas temperature. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope. Using this method, we have developed nanotube tips and nanotube tweezers that operate in a scanning probe microscope. The nanotube probes have been applied for observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have demonstrated their motion in scanning-electron-microscope and operated to carry nanomaterials in a scanning probe microscope.
AFM-Based Surface Potential Measurements on Carbon Nanotubes
Authors: Schujman Sandra B. , Vajtai Robert , Shusterman Yuriy , Biswas Sujit , Dewhirst Brian , Schowalter Leo J. , Wei Bin Q. , Ajayan Pulickel M. 
Published: April 2011

AbstractIn order to build electrical devices based on carbon nanotubes, it is crucial to understand the effects of the substrate, electrical contacts, defects and junctions on the transport properties of both multi-wall and single-wall carbon nanotubes (MWNT and SWNT). In the present study two different dispositions are analyzed. In one of them, isolated MWNT were deposited onto an insulating oxide layer over a conducting substrate and platinum electrical contacts were prepared via a focused ion beam (FIB) deposition method. An ohmic contact to the substrate allowed us to polarize it at a different potential than the nanotubes themselves. In the second one, a vertical array of MWNT was grown on a template of alumina in which one of the ends was coated with gold, to provide an electric contact. To investigate transport properties, we used an atomic force microscope (AFM) to determine the electric surface potential of MWNT. The technique employed, scanning surface potential microscopy (SSPM), applied a dc-voltage to the tip that equilibrates the local electrostatic potential on the sample so as to eliminate forces on the AFM tip caused by electric repulsion or attraction between tip and sample. There is no alteration of the sample potential caused by the tip. Surface potential measurements on the first system show that the electric transport on the MWNT has a diffusive character. The application of a (4.5V) bias between nanotube and substrate causes the resistance of the nanotube to drop by a factor of four. We can also resolve the voltage drop on the nanotube and at the contacts. The measurements in the second system (vertical arrangement) show that the nanotubes are uncapped and we can observe a contrast that varies with the application of different voltages to the back contact.
MRS 2001 (Boston): Design and Quantification of a Nanoscale Field Effect Transistor: Distributed Response Analysis for Investigating Conductive Behaviour.
Authors: Panhuis Marc in het , Coleman Jonathan N. , Popelier Paul. A. , Foley Brian , Munn Robert W. , Blau Werner J. 
Published: April 2011

AbstractA new design for a field effect transistor able to push back the physical limits of Moore's Law is described. An ab initio computational approach is presented that can be further developed to characterize the ON/OFF states of such a device. Distributed response analysis (M. in het Panhuis, P.L.A. Popelier, R.W. Munn, J.G. Ágyán (2001), J. Chem. Phys. 114, 7951-7961) is employed to investigate conductive behavior. The method demonstrates that in analogy to conduction an electron can move across a possible conjugated molecular switching element (para-nitroaniline) in an electric field.
Reproducible Synthesis of C60@SWNT in 90% Yields
Authors: Smith Brian W. , Russo Richard M. , Chikkannanavar S.B. , Stercel Ferenc , Luzzi David E. 
Published: April 2011

AbstractIn previous works, we have shown our discovery of C60@SWNT and first described the general mechanism of filling, which involves the vapor phase transport of C60 molecules to openings in the SWNTs' walls. Here, we discuss the high-yield synthesis of C60@SWNT by refinements to our method. Yields are measured by a calibrated weight uptake technique, a methodology that is not subject to many of the potential pitfalls inherent to other techniques that have been applied. At certain processing conditions, yields exceeding 90% were obtained and corroborated by transmission electron microscopy. From our data, we determine the parameters most important for creating endohedral SWNT supramolecular assemblies by the vapor phase method. Our results pave the way for successful single-tube measurements and for high-yield filling with non-fullerenes.
Effects of Fe film Thickness and Ammonia on the Growth Behavior of Carbon Nanotubes grown by thermal Chemical Vapor Deposition
Authors: Sohn Jung Inn , Choi Chel-Jong , Seong Tae-Yeon , Lee Seonghoon 
Published: April 2011

AbstractThe growth behaviour of carbon nanotubes on the Fe-deposited Si (001) substrates by thermal chemical vapor deposition (CVD) has been investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Fe films are deposited for 20 s–20 min by pulse-laser deposition. SEM results show that the growth characteristics of carbon nanotubes strongly depend on the Fe film deposition time. TEM and SEM results show that the pretreatment annealing at 800 °C causes the continuous Fe films to be broken up into nanoparticles 8–50 nm across and discontinuous islands 100 nm– 1.1 μm in size. It is shown that the Fe nanoparticles are essentially required for the formation of aligned carbon nanotubes. SEM results show that the growth behaviors of carbon nanotubes are strongly dependent on the pretreatment atmospheres. In addition, for the Ar gas-pretreated sample, a carbonaceous layer is formed near the surface region. TEM results show direct evidence that a base growth mode is responsible for the growth of carbon nanotubes in the present work. Based on the microscopy results, the pretreatment condition dependence of the growth behaviors of carbon nanotubes is discussed.
Plasma Enhanced Chemical Vapour Deposited Carbon Nanotubes for Field Emission Applications
Authors: Teo K. B. K. , Pirio G. , Lee S.B. , Chhowalla M. , Legagneux P. , Nedellec Y. , Hasko D.G. , Ahmed H. , Pribat D. , Amaratunga G.A.J. , Milne W.I. 
Published: April 2011

AbstractPlasma Enhanced Chemical Vapour Deposition is an extremely versatile technique for directly growing multiwalled carbon nanotubes onto various substrates. We will demonstrate the deposition of vertically aligned nanotube arrays, sparsely or densely populated nanotube forests, and precisely patterned arrays of nanotubes. The high-aspect ratio nanotubes (~50 nm in diameter and 5 microns long) produced are metallic in nature and direct contact electrical measurements reveal that each nanotube has a current carrying capacity of 107-108 A/cm2, making them excellent candidates as field emission sources. We examined the field emission characteristics of dense nanotube forests as well as sparse nanotube forests and found that the sparse forests had significantly lower turn-on fields and higher emission currents. This is due to a reduction in the field enhancement of the nanotubes due to electric field shielding from adjacent nanotubes in the dense nanotube arrays. We thus fabricated a uniform array of single nanotubes to attempt to overcome these issues and will present the field emission characteristics of this.
Effects of Ion Irradiation on Supported Carbon Nanotubes and Nanotube-Substrate Interfaces
Authors: Krasheninnikov A. V. , Nordlund K. , Keinonen J. 
Published: April 2011

AbstractWe employ molecular dynamics to study the effects of ion irradiation on carbon nanotubes lying on different substrates. We show that defect production depends on the type of the substrate and that the damage is higher for metallic heavy-atom substrates than for light-atom substrates, since in the former case sputtered metal atoms and backscattered recoils produce extra damage in the nanotube. We further study the behavior of defects and demonstrate that although ions may severely damage nanotubes in a local region, the nanotube carbon network can heal such a strong localized damage due to defect migration and dangling bond saturation. Finally, we predict the pinning of nanotubes to substrates by forming nanotube-substrate bonds which appear near irradiation-induced defects.
Magnetic Anisotropy of Cerium Endohedral Metallofullerene
Authors: Inakuma Masayasu , Enoki Toshiaki , Kato Haruhito , Shinohara Hisanori 
Published: April 2011

AbstractThe magnetic properties of Ce@C82 have been studied. The magnetic anisotropy of Ce@C82 was analyzed taking account of the crystal field of the interior C82 cage acting on Ce3+ ion. Results showed that the reduction of the susceptibility at low temperature was caused due to the antiferromagnetic coupling between Ce3+ ion and C82 cage. The magnetization measurement at several temperatures also supported the antiferromagnetic interaction at low temperature. The magnetic susceptibility larger than the calculated one was measured at higher temperatures due to the magnetic interaction between the metallofullerenes and between the particles in the crystal. The magnetization of some frozen Ce@C82 solutions was found to depend on the applied field magnitude. The dependence suggested that the magnetic anisotropy of Ce ion induced a torque to restrict the rotational motion of Ce@C82 by the field.
Thermodynamic Analysis of Carbon Nucleation on a Metal Surface
Authors: Kuznetsov Vladimir L. , Usoltseva Anna N. , Chuvilin Andrew L. , Obraztsova Elena D. , Bonard Jean-Marc 
Published: April 2011

AbstractA thermodynamic analysis of the carbon nucleation on the metal surface was performed. From the consideration of the catalytic mechanisms of carbon deposit formation on the metal surface we concluded that majority of these mechanisms include some common steps. The most important of them is the step of nucleation of carbon deposit on the metal surface. The master equation for the dependence of critical radius of the nucleus on reaction parameters was obtained. This equation demonstrates that a variation of the reaction parameters, such as the temperature, the nature of metal catalyst and the degree of supersaturation of the metal-carbon solution, can lead to the formation of different carbon deposits, such as filamentous carbon, multi-wall nanotubes (MWNT) or single-wall nanotubes (SWNT). The analysis performed allows us to conclude that for selective production of SWNT the nucleation must proceed at high temperature on the surface of liquid metal particles (Fe, Co, Ni). For solid metal particles (Mo) a high degree of supersaturation with carbon is also required.
Large-Area Deposition of Carbon Nanotubes for Field Emission Displays
Authors: Park Young-Jun , Han In-Taek , Kim Ha-Jin , Woo Yun-Sung , Lee Nae-Sung , Jin Yong-Wan , Jung Jae-Eun , Park Chong-Yun , Kim Jong-Min 
Published: April 2011

AbstractA direct synthesis of carbon nanotubes (CNTs) on substrates by chemical vapor deposition (CVD) is one of highly probable routes to reach their application to field emission displays. Several stringent requirements are prerequisite for this purpose, including low temperature growth below 600°C to engage glass substrates and large area deposition for practical use. This study carried out synthesis of CNTs by thermal CVD on glass substrates at temperatures as low as 500~550°C. CNTs were grown by thermal decomposition of CO and H2 gases at an atmospheric pressure for different thickness of Invar (an Fe-Ni-Co alloy ) catalytic layers. The growth of CNTs was strongly correlated with preparation of catalytic layers. The diameters and heights of as-grown CNTs increased as the catalytic layers became thicker from 2nm to 30nm. Measurements of the field emission properties of CNTs showed that the threshold electric fields were lowered with increasing thickness of catalytic layers. A uniform electron emission was observed over a large area of 150 × 150mm2, with high emission currents and high brightness.
Binary Phase of Layered Nanotubes
Authors: Whitby R.L.D. , Hsu W.K. , Boothroyd C.B. , Fearon P.K. , Kroto H.W. , Walton D.R.M. 
Published: April 2011

AbstractA binary phase of layered nanotubes, where MWCNs (Multi-walled carbon nanotubes) are coated by WS2, are generated by pyrolysing WO3-coated MWCNs in an H2S/N2 atmosphere at 900 °C. TGA and TEM show that WS2 acts as an antioxidant with respect to the MWCN core.
Utilizing Old Egyptian Wisdom for Stabilization of Individual Carbon Nanotubes in Aqueous Dispersions
Authors: Bandyopadhyaya Rajdip , Nativ-Roth Einat , Regev Oren , Rozen Rachel Yerushalmi 
Published: April 2011

AbstractThe tendency of single wall carbon nanotubes to organize into crystalline ropes and the aggregation of the ropes into tangled networks act as an obstacle for most applications, and diminishes the special properties of the individual tubes. We describe a procedure for dispersing as-produced nanotube powder in aqueous solutions of Gum Arabic. Dispersion results in spontaneous exfoliation of nanotubes ropes into individual tubes, as demonstrated via x-ray scattering and electron microscopy.
Self-Assembling and Ordering of Ge/Si Quantum Dots on Flat and Nanostructured Surfaces
Authors: Motta N. , Sgarlata A. , Balzarotti A. , Rosei F. 
Published: April 2011

ABSTRACTWe have studied by Scanning Tunneling Microscopy (STM) the effect of step bunching on Ge/Si(111) epitaxy. We have verified that self-organization of Ge islands is greatly influenced by “step bunching” which arises from the flash-annealing procedure used to reconstruct the Si surface. Two different growth regimes arise: initially islands nucleate and evolve only at steps, up to complete ripening; subsequently the same evolution is observed on flat areas of the sample. The average distance between islands and steps is nearly constant, originating a single row of equally spaced islands, followed by other rows of islands in between. The exploitation of this phenomenon, which is governed by the surface diffusion length of Ge on Si (estimated from our data) and by the terrace width, constitutes one possible path to achieve self-organization of quantum dots.
Optical Characterization of Cadmium Telluride Doped Heterostructured Opaline Photonic Crystal
Authors: Solovyev V. G. , Romanov S.G. , Sotomayor Torres C.M. , Gaponik N. , Eychmüller A. , Rogach A. L. 
Published: April 2011

ABSTRACTA double-layer photonic crystal (PhC) possessing incomplete photonic band gap (PBG) has been prepared by successive formation of one opaline film on top of another and subsequent impregnation with CdTe colloidal nanocrystals as the light source. Transmission, reflection and photoluminescence (PL) spectra of this nanocomposite have been measured from 1.8 to 2.5 eV at different angles of the light incidence and detection. The suppression of emission intensity has been found at both stop bands of the PhC heterostructure. Depending on the excitation power, either suppression or enhancement of the emission rate at the stop band has been observed.
The Role of the Interfaces in the Optical Effects of Large-Sized SiCxO1-xN Nanocrystallites
Authors: Plucinski K.J. , Kaddouri H. , Kityk I.V. 
Published: April 2011

ABSTRACTThe band energy structure of large-sized (10-25) nm nanocrystallites (NC) of SiCxO1-xN (0.96<x>1.06) was investigated using different band energy approaches, as well as modified Car Parinello molecular dynamics simulations of interfaces. A thin carbon sheet (of about 1e nm) appears, covering the crystallites. This sheet leads to substantial reconstruction of the near-the-interface SiCxO1-xN crystalline layers. Numerical modeling shows that these NC may be treated as quantum dot-like SiCxO1-xN reconstructed crystalline surfaces, covering the appropriate crystallites. All band energy calculation approaches (semi-empirical pseudopotential, fully augmented plane waves and norm-conserving self-consistent pseudopotential approaches) predicted the experimental spectroscopic data. In particular, it was shown that the near-the-surface carbon sheet plays a dominant role in the behavior of the reconstructed band energy structure. Independent evidence for the important role of the dot-like crystalline layers are the excitonic-like states, which are not dependent on the particular structure of the SiC, but are sensitive to the thickness of the carbon layer.
Surfactant Templated Assembly of Hexagonal Mesostructured Semiconductors Based on [Ge4Q10]4- (Q=S, Se) and Pd2+ and Pt2+ ions.
Authors: Trikalitis Pantelis N. , Rangan Krishnaswamy K. , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACT4-Mesostructured semiconducting non-oxidic materials were prepared by linking [Ge4Q10]4- (Q=S, Se) clusters with the square planar noble metal cations of Pd2+ and Pt2+ in the presence of cetylpyridinium surfactant molecules. The use of Pt2+ afforded materials with exceptionally high hexagonal pore order similar to those of high quality silica MCM-41. These materials are semiconductors with energy band gap in the range 1.8<Eg<2.5 eV.