bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvothermal Synthesis Of Electrochemically Active Nanocrystalline Li-Ti-O Spinel
Authors: Fattakhova Dina , Krtil Petr 
Published: April 2011

ABSTRACTNanocrystalline Li-Ti-O spinel samples were prepared by solvothermal reaction of TiO2 with lithium hydroxide in water and ethanol. The hydrothermal reaction proceeds at temperature higher than 130 °C. The reaction proceeds via dissolution-precipitation mechanism and its course is not sensitive to titanium dioxide polymorph used in the reaction. Product of the reaction in water has cubic rock salt type structure. It converts, however, to spinel if annealed to temperatures exceeding 250 °C. The re-crystallization is accompanied with water removal from the structure. Solvothermal reaction in ethanol leads directly to a product with spinel structure without need for annealing. Both products are active for Li insertion; theelectrochemical activity. The specific capacity ranges between 100 and 160 mAh/g depending on the annealing temperature.
Casimir Forces between ThermallyActivated Nanocomposites
Authors: Esquivel-Sirvent Raúl , Villarreal Carlos , Noguez Cecilia 
Published: April 2011

ABSTRACTWe present a theoretical study of the modification of Casimir forces between nanocomposite slabs that exhibit a metal-dielectric transition. In particular, we consider slabs made of VO2 precipitates in sapphire, whose effective dielectric function is calculated within a mean field approximation. The results for the Casimir force as a function of the separation of the slabs, show that at a fixed separation the magnitude of the force changes as temperature increases from 300 K to 355 K. The possible applications of these results to Casimir devices is discussed.
Production and Magnetic Properties of Nanocomposites made of Ferrites and Ceramic Matrices
Authors: Calderon H. A. , Huerta A. , Umemoto M. , Cornett K. 
Published: April 2011

ABSTRACTThis investigation deals with the production of materials containing a dispersion of magnetic nanoparticles in an insulating matrix. Such a distribution of magnetic centers is expected to absorb electromagnetic radiation in a range of wavelengths. Wüstite-magnetite and magnesiamagnesioferrite nanocrystalline ceramics have been prepared by mechanical milling and spark plasma sintering. As-milled powders have a nanocrystalline structure in both systems. Low energy milling gives rise to an increasingly higher volume fraction of wüstite as a function of milling time in the Fe1-xO-Fe3O4 system. Similar results are obtained in the MgO-MgFe2O4 system with increasingly larger amounts of MgFe2O4 produced by milling. Composites of magnetic particles (Fe3O4 or MgFe2O4) in a nonconductive matrix (FeO or MgO, respectively) are found in the sintered samples. Measurement of magnetic properties can be used to determine conclusively the nature of the developed phases and the effect of grain size.
Vanadium Oxide Nanotubes: Characterization and Electrochemical Behavior
Authors: Lutta Samuel T. , Dobley Arthur , Ngala Katana , Yang Shoufeng , Zavalij Peter Y. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTVanadium oxide nanotubes (VONT) were formed from vanadium (V) oxide and the dodecylamine templating agent by a sol-gel reaction and subsequent hydrothermal treatment. The nanotubes were characterized by transmission electron microscopy (TEM), electron diffraction, thermogravimetric analysis (TGA), infrared spectroscopy and powder X-ray diffraction (XRD). The nanotubes consist of VO2.4[C12H28N] 0.27 and range in diameter from 100 nm to150 nm. The study further reveals that the compound maintained the tubular morphology when heated at 430o C in an inert atmosphere. However, the tubular morphology is destroyed when the compound is heated at about 130°C in oxygen. Organic free manganese intercalated vanadium oxide nanotubes (MnVONT) were synthesized by an ion exchange reaction. The previously mentioned techniques were used to characterize MnVONT. Mn0.86V7O16+δ. nH2O layers have 2D tetragonal cell with a=6.157(3) Å, while interlayer spacing is 10.52 (3) Å. VONT, heated VONT and Mn0.86V7O16+δ. nH2O are redox - active and can insert lithium reversibly. This study reveals that the electrochemical performance of VONT is enhanced by removing the organic template by heating in an inert atmosphere or exchanging with Mn2+ ions.
Thermal and Structural Characterization of Nanocomposite Iron Nitride - Alumina and Iron Nitride - Silica Particles
Authors: Viano Ann M. , Mishra Sanjay R. 
Published: April 2011

ABSTRACTNanocomposite iron nitride based powders are known to have enhanced magnetic and other physical properties. To further explore their potential for application in various fields, we have performed a systematic study of the iron nitride - alumina and iron nitride - silica systems. Iron nitride powder of composition FexN (2 < x < 4), containing both Fe3N and Fe4N phases, was mechanically milled with Al2O3 or SiO2 powder for 4, 8, 16, 32, and 64 hours at the following compositions; (FexN)0.2(Al2O3)0.8, (FexN)0.6(Al2O3)0.4, (FexN)0.2(SiO2)0.8, and (FexN)0.6(SiO2)0.4. Differential thermal analysis and X-ray diffraction were performed to investigate thermal and structural transitions as a function of milling time. As the milling time is increased, the thermal peak corresponding to Fe4N is diminished, while the one corresponding to Fe3N is enhanced. These transitions are correlated with X-ray diffraction patterns. All XRD peaks broaden as a function of milling time, corresponding to smaller particle size. Transmission electron microscopy also reveals a decrease in particle size as the milling time in increased.
Single Particle and Ensemble Spectroscopy of Silicon Nanoparticles
Authors: Pell Lindsay E. , Yu Zhonghua , English Douglas S. , O'Connor Don , Barbara Paul F. , Korgel Brian A. 
Published: April 2011

AbstractOctanethiol-stabilized Si nanocrystals, ranging from 2 to 8 nm in diameter, were synthesized in cyclohexane heated and pressurized above its critical point at temperatures ranging from 400°C to 500°C. The nanocrystals exhibit crystalline cores and photoluminesce with relatively high efficiencies. These nanocrystals are suitable for single particle spectroscopic measurements that reveal optical information about the individual chromophores that are buried in ensemble measurements. The sterically-stabilized Si nanocrystals emit with relatively narrow emission spectra at room temperature, characteristic of molecules.
Laser Cleaning of Nanoparticles from Solid Surfaces
Authors: Lu Y.F. , Zheng W.Y. , Zhang L. , Luk'yanchuk B. , Song W.D. , Wang W.J. , Hong M.H. , Chong T.C. 
Published: April 2011

AbstractThe experimental analysis of dry laser cleaning efficiency is done for certified spherical particle (SiO2, 5.0, 2.5, 1.0 and 0.5 μm) from different substrates (Si, Ge and NiP). The influence of different options (laser wavelength, incident angle, substrate properties, i.e. type of material, surface roughness, etc.) on the cleaning efficiency is presented in addition to commonly analyzed options (cleaning efficiency versus laser fluence and particle size). Found laser cleaning efficiency demonstrates a great sensitivity to some of these options (e.g. laser wavelength, angle of incidence, etc.). Partially these effects can be explained within the frame of the Mie theory of scattering. Other effects (e.g. influence of roughness) can be explained along the more complex line, related to examination of the problem “particle on the surface” beyond the Mie theory. 0.5 μm spherical silica particles were placed on Silicon (100) substrate. After laser irradiation with a 248 nm KrF excimer laser, hillocks with size of about 100 nm were obtained at the original position of the particles. Mechanism of the formation of the sub-wavelength structures were investigated and found to be the near-field optical resonance effect induced by particles on surface. Theoretical prediction of the near-field light intensity distribution was presented, which was in agreement with the experimental result.
Self – Assembling of Nanoparticles in the form of Double Linear Chains and Superlattices on Their Basis
Authors: Malkhasyan R.T. , Karakhanyan R.K. , Nazaryan M.N. , Sung C. 
Published: April 2011

AbstractThe self-assembling systems in nanoscale powders of crystalline MoO3 are disclosed. For the first time, the double linear chain aggregates of the MoO3 nanoparticles were revealed in nanoscale powders of MoO3, treated by vibrationally excited molecules of hydrogen. Double linear chain aggregates form a linear and an orthogonal supperlattices. Both the double linear chain aggregates and the supperlattices formed are being considered as self-assembling systems. The treatment of the powders by the molecules of hydrogen is a method of obtaining long self-assembling chains of inorganic materials and supperlattices on their basis.
Precipitation of Nanoscale Hydrous Alumina from Sodium Aluminate Solutions
Authors: Das Biman , Graeffe Mats , Toscano Alicia , Brancewicz Chris , Rasmussen Don H. 
Published: April 2011

AbstractSodium aluminate liquor was diluted and neutralized with water and oxalic acid in the presence of surface-active polymers polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and sodium carboxymethylcellulose (NaCMC). Dynamic light scattering experiments showed that the final precipitate had diameters between 80 – 300 nm when precipitated in the presence of PVP, and 600 – 800 nm when precipitated in the presence of NaCMC. The initial sols prepared using oxalic acid without surfactant had diameters of 200 – 300 nm. Scanning Electron Microscopy, SEM, Energy Dispersive Analysis by X-rays, EDAX, and X-ray diffraction were used for imaging, chemical and structural analysis of the final dialyzed particles. Transmission Electron Microcopy, TEM, images of the sols trapped and dried between nitrocellulose membranes showed that the initial particles were nearly spherical and bimodal in particle size. Larger particles had diameter of about 176 nm but were not pure solid alumina. A small fraction of initial particles had diameters much smaller than 176 nm. The discrepancies between initial and final precipitates indicate a complex precipitation pathway.
Electronic States of Mn2+ in ZnS:Mn Nanoparticle Examined by EPR Measurements and Molecular Orbital Calculation
Authors: Nagare Sanshiro , Isobe Tetsuhiko , Senna Mamoru 
Published: April 2011

AbstractThe discrete variational Xα method was introduced to elucidate the possible factors of luminescence enhancement of ZnS:Mn modified by poly acrylic acid. The effective charge calculation of Mn indicated that the ionicity of Mn and its first neighbors increase when Mn atom is located at the surface site rather than in the bulk, in accordance with the signals observed from EPR measurements. The bond order between Mn and S increased by the stronger exchange interaction when Mn was oxidized by coordination of carboxyl group rather than by adsorption of OH or a SH group. The bond order between Mn and O is higher for the same situation, which may attribute to the energy transfer from poly acrylic acid to ZnS:Mn. As a consequence, the symmetry of the d orbital decreased, judging from the contour maps of the molecular orbital. This relaxed the forbidden d-d transition of Mn2+ and resulted in the enhanced photo luminescence.
The Consolidation Behavior of L12 Phase Al3Zr & (Al+12.5at%)3Zr Powders with Nanocrystalline Structure During Spark Plasma Sintering
Authors: Moon Kyoung Il , Kim Seung Chul , Lee Kyung Sub 
Published: April 2011

AbstractThe spark plasma sintering (SPS) of L12 phase Al3Zr and (Al+12.5at.%Cu)3Zr powders with a nanocrystalline microstructure has been studied to produce bulk intermetallic compounds which maintain metastable structures such as L12 structure and nanocrystalline microstructure. The powders were prepared by 10 h planetary ball milling (PBM). Full-density L12 (Al+12.5at.%Cu)3 Zr intermetallic compounds were obtained by SPS for 0 min. at 600°C. The smallest grain size was obtained in the specimen prepared at 600°C for 0 min., which was 20-30 nm as confirmed by TEM observation. Accordingly, the highest micro-hardness, 989.5 HV, was obtained in the specimen and this value was three times higher than those of the specimens with micro grain sizes. Full density Al3Zr intermetallics were prepared by SPS at 700°C for 0 min.. However, their crystal structure was D023 and micro-hardness was 778.1 HV. By using SPS, the sintering time can be reduced within 10 min.
Shock-Wave Synthesis of Nanoparticles During Ion Sputtering
Authors: Rehn L. E. , Birtcher R. C. , Donnelly S. E. , Baldo P. M. , Funk L. 
Published: April 2011

AbstractWe report electron microscopy studies of nanoparticles ( 500 ≤ n ≤ 104, where n is the number of atoms in a given cluster) that are sputtered from the surface by high-energy ion impacts. Measurements of the sizes of these clusters yielded an inverse power-law distribution with an exponent of –2 that is independent of irradiating ion species and total sputtering yield. This inverse-square dependence indicates that these nanoclusters are produced when shock waves, generated by sub-surface displacement cascades, impact and ablate the surface. Such nanoparticles consist of simple fragments of the original surface, i.e., ones that have not undergone any large thermal excursion. As discussed below, this “ion ablation” technique should therefore be useful for synthesizing nanoparticles of a wide variety of alloy compositions and phases.
Processing Complex and Uniform Nanoparticles for Microelectronic and Photonic Applications
Authors: Kambe Nobuyuki 
Published: April 2011

AbstractTwo major challenges that exist in order to utilize nanoparticles as building blocks for microelectronic and photonic applications are presented. The first challenge is how to make uniform nanoparticles in industrial-scale. The second challenge is how to convert these nano-building blocks to application forms such as device structures or coatings. In this paper, materials and processing guidelines to provide the solutions for these challenges are described on the basis of (a) laser-driven chemical reaction processes to generate a versatile range of nanoparticles having extremely narrow size distributions, and (b) unique organic-inorganic nanocomposites using surface engineering over nanoparticles. As promising applications, direct deposition of nanoparticles and nanocomposites are discussed in conjunction with planar lightwave devices, photonic nanocomposites for the refractive index engineering, and planarization processes for electronic chips.
Microstructural Investigation of Grain Growth in Cryomilled Inconel 625 Powder
Authors: Chung Kyung H. , Lee Jongsang , Rodriguez Rodolfo , Lavernia Enrique J. 
Published: April 2011

AbstractThe grain growth behavior of cryomilled nanocrystalline Inconel 625 powders was investigated during isothermal heat treatment at 600 ∼ 900 °C for 1 ∼ 4 hours. The grain size of cryomilled Inconel 625 remained under 250 nm following heat treatment in the temperature range of 600 ∼ 900 °C up to 4 hours, which represents an improved grain stability compared to that of conventional Inconel 625 and cryomilled pure Ni. Microstructural studies, using TEM, revealed the existence of oxide particles after cryomilling. The pinning effects on grain stability by oxide particles were quantitatively analyzed. The grain stability of cryomilled Inconel 625 powders at 900 °C was noted to be better than that at lower temperatures. This behavior was attributed to the presence of two types of precipitates found at this temperature, which were identified as spherical NbC and rod shaped Ni3Nb intermetallic precipitates. These precipitates promote grain growth resistance at this particular temperature via a grain boundary pinning mechanism. The preferred nucleation sites of those precipitates was noted to be at grain boundaries, thereby augmenting the grain boundary pinning effect.
Quenching Phenomena in Water-Soluble CdSe/ZnS Quantum Dots
Authors: Speckman D.M. , Jennings T.L. , LaLumondiere S.D. , Moss S.C. 
Published: April 2011

AbstractSemiconductor nanocrystals are expected to play an important role in the development of novel electronic and optoelectronic devices, and have already shown promise in the area of biological reporters for medical screening and sensor applications. We have been involved in developing luminescent CdSe/ZnS core-shell nanocrystals (or quantum dots, QDs) for use in self-assembled structures and as fluorescent reporters in immunoassay-based biodetectors. As part of our efforts to bind semiconductor CdSe/ZnS quantum dots to antibody proteins for our immunoassay work, we functionalized the nanocrystal surfaces with a variety of organic acid salts to impart water solubility to the nanocrystals.During the course of working with these derivatized, water-soluble quantum dots, we observed significant differences in their chemical reactivities and physical characteristics compared to those of underivatized CdSe/ZnS nanocrystals. One of the most striking differences observed is the reactivity of the derivatized and underivatized nanocrystals with stainless steel surfaces. The fluorescence of aqueous mixtures of our water-soluble nanocrystals is immediately quenched upon exposure of the mixtures to stainless steel (SS) surfaces or to chromium oxide, whereas underivatized quantum dots exhibit little or no reactivity at all. As has been reported by several other laboratories, the water-soluble nanocrystals also exhibit significantly lower quantum yields compared to the underivatized nanocrystals. We discuss the unusual reactivity exhibited by these nanocrystals, and suggest possible explanations for their interesting chemical behavior. We also describe methods to prevent the quenching of water-soluble derivatized quantum dots by stainless steel and metal oxides.
Photoemission Study of Thiol-Capped Gold Nanoparticles
Authors: Nagasawa Tazumi , Tanaka Akinori , Sasaki Hiroyuki , Kuriyama Yosuke , Suzuki Shoji , Sato Shigeru , Sekine Tsutomu 
Published: April 2011

AbstractA photoemission study of dodecanethiol (DT)-capped Au nanoparticles on the highly oriented pyrolytic graphite (HOPG) substrates has been carried out in order to investigate in detail the electronic structures of metallic nanoparticles supported on the substrates. The present DT-capped Au nanoparticles show that the leading edge in the photoemission spectra near the Fermi level is not the Fermi edge, with the midpoint of the steep slope being away from the Fermi level. From these results, we discuss the electronic structures of DT-capped Au nanoparticles, especially nanoparticle-HOPG substrate interaction.
Carbon Nanotube Anodes for Lithium Ion Batteries
Authors: Raffaelle Ryne P. , Gennett Thomas , Maranchi Jeff , Kumta Prashant , Hepp Aloysius F. , Heben Michael J. , Dillon Anne C. , Jones Kim C. 
Published: April 2011

AbstractHighly purified single-wall carbon nanotubes (SWCNT) were investigated for use as an anode material for thin film lithium ion batteries. The high purity nanotubes were obtained through chemical refinement of soot generated by pulsed laser ablation. The purity of the nanotubes was determined via thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. The specific surface area and lithium capacity of the SWCNT's was compared to that of other conventional anode materials (i.e., carbon black, graphite, and multi-walled carbon nanotubes). The Brunauer, Emmett, and Teller (BET) technique based on nitrogen adsorption was used to measure the specific surface area of the various anode materials. The SWCNT's exhibited a specific surface area on the order of 915 m2/g, much higher than the other carbonaceous materials. Cyclic voltammetric behavior and the lithium-ion capacity of the materials were measured using a standard 3-electrode electrochemical cell. The cyclic voltammetry showed evidence of “staging” that was similar to other carbonaceous materials. The electrochemical discharge capacity of the purified single walled carbon nanotubes was in excess of 1300 mAh/g after 30 charge/discharge cycles when tested using a current density of 20μA/cm2.
CFD Analysis on a Vortex Enhanced CVD Reactor Design
Authors: Kuwana Kazunori , Andrews Rodney , Grulke Eric A. , Saito Kozo 
Published: April 2011

AbstractTo enhance the yield of multi-walled carbon nanotubes (MWNTs), a vortex enhanced CVD reactor (VECVD) design has more advantage over the conventional straight tube CVD. A computational fluid dynamics (CFD) code was applied to analyze heat and mass transfer processes to compare the conventional CVD design performance with a new type. The calculation showed that VECVD has a stronger and more uniform circulation along the reactor than the conventional CVD design.
Orientational Growth of Carbon Nanotube by Thermal CVD
Authors: Zhu Shen , Su Ching-Hua , Cochrane J. C. , Gorti S. , Lehoczky S. , Cui Y. , Burger A. 
Published: April 2011

AbstractCarbon nanotubes are synthesized using thermal chemical vapor deposition. Various temperature and pressure are used to fabricate carbon nanotubes. It is found that the nanotube-diameter distribution mainly depends on the growth-temperature. With the substrate surface normal either along or against the gravity vector, different growth orientations of multi-walled carbon nanotubes are observed by scanning electron microscopy although the Raman spectra are similar for samples synthesized at different locations. The sizes of these carbon nanotubes in each sample are quite uniform and the length of the tube is up to hundreds of micrometers. These results suggest the gravitation effects in the growth of long and small diameter CNT.
Single Wall Carbon Nanotubes Filled with Metallocenes: a First Example of Non-Fullerene Peapods
Authors: Stercel F. , Nemes N. M. , Fischer J. E. , Luzzi D. E. 
Published: April 2011

AbstractWe report the synthesis and analysis of metallocenes (ferrocene, chromocene, ruthenocene, vanadocene, tungstenocene-dihydride) encapsulated in single wall carbon nanotubes (SWNTs). In the case of ferrocene, efficient filling of the SWNTs was accomplished from both the liquid and the vapor phase. The other two metallocenes were filled from the vapor phase. High resolution transmission electron microscopy reveals single molecular chains of metallocenes inside SWNTs. Molecules move under the electron beam in the SWNTs indicating the absence of strong chemical bonds between each other and the SWNT wall. Their movement freezes after short illumination as a result of irradiation damage. Energy dispersive X-ray spectrometry confirms the presence of iron, chromium, ruthenium, vanadium and tungsten.
Light Pulse Propagation in Three-Dimensional Photonic Crystals
Authors: Kitano H. , Minami F. , Sawada T. , Yamaguchi S. , Ohtaka K. 
Published: April 2011

ABSTRACTThe phase characteristics of transmitted optical pulses in three-dimensional photonic crystals were investigated in the frequency and time domain by using the spectrally resolved cross-correlation technique. The temporal evolution of femtosecond pulses passing through polystyrene colloidal crystals exhibits a large phase distortion near the stop bands. The phase discontinuity around the band gap was observed in the frequency-domain. The phase of the transmitted pulses is found to change by p across the band gap. The dispersion curve estimated from the phase shift shows good correspondence with those calculated from a photonic band calculation. The group velocity significantly slows down near the stop bands. A large change of the group velocity dispersion is also observed near the band edges. These results are in good agreement with the band theory.