bluuebunny/crossref_metadata_2025 huggingface dataset:
Anomaly of Thermal Properties in Thin Films of La1-xSrxCoO3 Series Synthesized with a Combinatorial Processing
Authors: Takata Yoshiaki , Adachi Yutaka , Haneda Hajime , Wada Yoshiki , Ohtani Makoto , Fukumura Tomoteru , Kawasaki Masashi , Koinuma Hideomi
Published: April 2011

The thermal diffusivities throughout a composition-spread film comprising La1- xSrxCoO3 series were determined by Transient Reflecting Grating (TRG) measurements. Thermal diffusivities of transparent SrCoO3 film and SrTiO3 substrate were determined by using third harmonics having wavelength of 266 nm as an excitation light with only a certain length of grating spacing. The thermal diffusivities of them were 0.02 and 0.05 cm2/s, respectively. With regard to untransparent thin films, the experiment was performed by setting three kinds of grating spacing for the excitation light having the fundamental wavelength, 800 nm in order to obtain high precision. The distribution profile of obtained values of the thermal diffusivity throughout the sample was traced as 0.06 - 0.18 - 0.01 cm2/s corresponding to the variation of in La1-xSrxCoO3, thus showing a convex profile, however, this anomalous profile was verified by comparing with the data obtained by the X-ray diffractometer.
Development of the Combinatorial Glass Formation Tester
Authors: Inoue Satoru , Todoroki Shin-ichi , Matsumoto Takehisa , Hondo Takaharu , Araki Tetsuo , Tsuchiya Toshio
Published: April 2011

The combinatorial glass formation tester has been developed to determine the glass forming regions as quickly as possible. The 24 glass batches of about 1g were put into each carbon crucible on a carbon holder and heated in an electric furnace filled with dry nitrogen gas. After about a half an hour heating, the crucibles were taken out from the furnace and moved into the cooling chamber purged with dry nitrogen gas. The holder and the crucibles were moved on to a cooling stage to be cooled down quickly with a water flowing jacket together with nitrogen gas blowing. The time interval after taking out of the crucibles till the placement on the cooling stage was shortened as much as possible, resulting to be 10sec. The temperature of the melt in the crucibles was measured with an optical pyrometer to estimate the cooling rate. The top view of the crucibles on the holder was taken with a CCD camera during cooling. The CCD figures were stored on a computer for the judgments of the transparency of the samples in the crucibles to compile a glass forming region. The glass formation tester can manage 24 glass melting tests every 1 hours. In other words, the tester can produce at least 192 glass samples (24 x 8=192) within a day working time. The speed was roughly 100 times larger than the case of manual operation.
Materials Development for Solid Oxide Fuel Cells Using Qualitative Models
Authors: Schmid Klaus , Krebs Volker , Krügel Albert , Ivers-Tiée Ellen , Schäfer Sven
Published: April 2011

Solid Oxide Fuel Cells (SOFC) are high temperature energy converters. When an SOFC is operated for the rst time, a substantial increase in cell performance is observed which is caused by microstructural changes at the cathode/electrolyte interface. To optimize the resulting formation of the interface, a dynamic model is required that represents the relations between materials compositions, operating conditions, electric current, and microstructure.

Building a model based on chemical reaction equations fails because of the high complexity of the interface reactions. Therefore, this contribution presents an interdisciplinary approach to modeling in materials development by applying computational intelligence techniques. Qualitative models are used to formalize the expert knowledge about the irreversible materials changes at the cathode/electrolyte interface. Fuzzy if-then rules represent the dynamic behavior of the microstructural formation. The resulting model enables the application of simulations instead of time-consuming experiments and thus allows the systematic optimization of the startup process.
The Influence of Many Body Interactions in the Stress-Velocity Relation of a Single Dislocation in a 2D Lattice.
Authors: Robles M. , Mustonen V. , Kaski K. , Patriarca M.
Published: April 2011

The stress-velocity relation of a single dislocation moving in a 2-D lattice has been studied using interactive molecular dynamic simulations. A hybrid interatomic model potential which couples Lennard-Jones(LJ) potential and the Embedded Atom Model (EAM) potential, is used to include radial and many body interactions. Both parts are assembled by a parameter so that the potential can be changed to describe a pure radial interaction to a strong many body interaction in a continuous way. Setting up a constant-stress scenario, the movement of a single dislocation is tracked from zero velocity state, up to a terminal velocity state. The external stress vs. terminal velocity curves have been obtained in the subsonic regime for different values of the coupling parameter. Non-linear relations are found velocity regime 0.1ct to 0.6ct, where ct is the transverse speed of sound. Results have been analyzed using an augmented Peierls model to seek the connection between atomic scale, continuum variables and the limiting speed of dislocations
Modeling Cascade Aging in Dilute Fe-Cu Alloys
Authors: Wirth B. D. , Odette G. R.
Published: April 2011

The continued safe operation of nuclear reactors and their potential for lifetime extension depends on ensuring reactor pressure vessel integrity. Reactor pressure vessels and structural materials used in nuclear energy applications are exposed to intense neutron fields that create highly non-equilibrium defect concentrations, consisting of a shell of self-interstitial atom and clusters surrounding a vacancy-rich core, over picosecond time scales. This spatially correlated defect production initiates a long chain of events responsible for microstructure evolution and hence irradiation embrittlement. In this paper, we describe the combined use of molecular dynamics (MD) and kinetic lattice Monte Carlo (KMC) to simulate the long-term rearrangement (aging) of displacement cascades in dilute Fe-Cu alloys. The simulations reveal the formation of a continuous distribution of three dimensional cascade vacancy-Cu cluster complexes and demonstrate the critical importance of spatial, as well as short and long-time correlated processes that mediate the effective production of primary defects. Finally, this approach can generate production cross-sections for vacancy-Cu clusters that can then be used in rate theory type models of long term global micro and microstructural evolution.
Phase Transformations Induced by Arsenic Implants into Silicon
Authors: Lavine James P. , Tuschel David D. , Black Donald L.
Published: April 2011

Micro-Raman spectroscopic investigations of arsenic-implanted silicon show lines characteristic of silicon crystallites even at implant doses above the amorphization threshold. The intensity and frequency of occurrence of the lines increase with the implanted dose. Polarization/orientation Raman studies indicate the crystallites are silicon in the hexagonal phase (Si-IV) and silicon in the diamond phase (Si-I). The latter are oriented differently than the substrate silicon. Monte Carlo simulations of the arsenic ion energy loss and published molecular dynamics studies suggest that each arsenic ion deposits sufficient energy to locally melt the silicon lattice. This is taken as the basis of the present attempt to explain the origin of the crystallites. A one-dimensional numerical model is developed to determine the time scale for the liquid silicon to solidify. The effect of amorphous silicon on the solidification is also investigated.
Keratin Protein Nano-fiber for Removal of Heavy Metals and Contaminants
Authors: Misra M. , Kar P. , Priyadarshan G. , Licata Carlo
Published: April 2011

Keratin protein fiber (AKF™) is a renewable source of biosorbent that can be used for filtration of heavy metal and nanosize contaminants. The major composition of keratin fiber is the structured protein micofibril, consisting of numerous nanosized pores. The combination of nanostructure and metal binding capacity protein sites make it an ideal material for removal of heavy metals from solutions. The mechanism of heavy metal uptake onto keratin protein involves a combination of several steps such as adsorption, precipitation, and ion exchange. Keratin protein has good tensile strength and is stable over a wide pH range.
A New Hybrid Aerogel Approach to Modification of Bioderived Polymers for Materials Applications
Authors: Wang Mingzhe , Liu Xipeng , Ji Shuang , Risen William M.
Published: April 2011

Novel hybrid aerogels consisting of the bioderived polymers chitosan, pectic acid or alginic acid and silica have been synthesized as clear monoliths from clear gels by supercritical fluid extraction. These renewable resource polymers, which are soluble and typically unassociated in aqueous systems, are separately arranged in aerogel scaffolding. This makes them exposed and available for reactions that in some cases would not be possible in aqueous systems. Thus, it is possible to react the amine groups of chitosan, a polymer derived from chitin, with isocyanate-terminated prepolymers to form urea linkages and to form new linked chitosan materials. Following the reactions, the scaffold can be dissolved and the new material isolated. Variations lead to hydrophobic or hydrophilic materials. The reactions of aerogel scaffolded bioderived polymers to form urethane-or amide-group linked materials also will be presented and the properties of newly formed materials will be described. Further reactions enabled by the approach, including ones leading to radiation curable polymeric systems will be presented.
Characterization of Renewable Composites
Authors: Emekalam A. , Gu X. , Raghavan D.
Published: April 2011

In this study, we demonstrate the usefulness of chemical based method in combination with AFM to characterize a wide range of degradable polymer blends. This approach is based on selective degradation of one of the phase in a multi-phase system and the ability of TMAFM to provide nanoscale lateral information about the different phases in the polymer system. Composite films containing different percentage of hydrolyzable polymer were either melt processed/solution casted and then exposed to a hydrolytic acidic environment and analyzed using TMAFM. Pits were observed to form in the blend films. The progressive hydrolysis of the hydrolyzable component in the composite was studied by FTIR analyses. TMAFM phase imaging was used to follow pit growth of the blend as a function of exposure time. The usefulness of the chemical modification/AFM approach in the characterization of renewable porous material membranes is discussed.
Injection Molding a Polyolefin-Based Nanocomposite versus a Talc-Filled TPO
Authors: Okonski David A.
Published: April 2011

General Motors Research and Development and Basell Polyolefins have jointly developed a family of polyolefin-based nanocomposites for use in the injection molding of body-side claddings. Basell Polyolefins commercialized one of these materials as Hifax DX277 in September of 2000, and General Motors has exclusive use of this material. Confidence in the ability of DX277 to perform as intended is being reinforced by molding trials at various Tier 1 locations. In addition to mass savings, the nanocomposite material is showing a much wider processing window than conventional talc-filled TPO’s – allowing Tier 1 molders the opportunity to process away problems rather than initiating a tooling change. This paper will describe the processing advantages associated with the injection molding of a polyolefin-based nanocomposite over a conventional talc-filled TPO.
Glass and glass-ceramic matrix composites: from model systems to useful materials
Authors: Boccaccini Aldo R. , Kaya Cengiz
Published: April 2011

By reinforcing glass and glass-ceramic matrices with ceramic or metallic fibres, advanced composite materials with improved mechanical properties can be fabricated. These composites were originally developed as model systems for laboratory-scale experiments. Due to their remarkable thermomechanical properties, however, the materials are candidate for a variety of technical applications. The present contribution is based on an extensive review of the available literature on these materials, accumulated in the last 30 years, focusing on manufacturing techniques. The literature analysis reveals that several challenges related to the composites fabrication remain for future developments. In particular, it is shown that relative limited R&D work has been carried out so far in the area of manufacturing of engineering components and structures having complex geometry and large dimensions. The application of electrophoretic deposition techniques in order to manufacture three-dimensional components, e.g. tubes, may represent a considerable improvement in this regard. The final goal of this report is to generate a broader interest in glass and glass-ceramic matrix composites both in the scientific and industrial communities, so that the high technological potential of these materials can be wider exploited.
A Novel Polyamide 12/Al-Cu-Fe Quasicrystal Composite
Authors: Liu Yuejian , Bloom Paul D. , Sheares Valerie V. , Otaigbe Joshua U.
Published: April 2011

The tribological and mechanical properties of a novel polyamide 12 (PA12)/Al-Cu-Fe quasicrystal (QC) composite were systematically studied to accelerate efforts to develop a useful, melt-processable, and wear-resistant polymer composite. The wear and friction properties were characterized using a pin-on-disk configuration and the static and dynamic mechanical properties were investigated using dynamical mechanical analyzer, tensile tester, and an impact tester. Further, the melt processability of the composite was studied using a Haake torque rheometer and a dynamic rotational rheometer. The results suggest that PA12/QC composite can be melt-processed into a wear-resistant material with enhanced mechanical properties for applications where combinations of wear resistance and good mechanical properties are required. The static mechanical properties of the composite were found to be consistent with the Halpin-Tsai equation and agreement was observed between the measured viscoelastic properties and theoretical predictions of Burgers' and Eilers' models.
Molecular Engineered Porous Nanocomposites of Metal Oxide and Clay Using Surfactants
Authors: Zhu Huai Y. , Lu Gao. Q.
Published: April 2011

A novel synthesis route of metal oxide nanoparticles dispersed in a silicate framework is reported here. This composite nanostructure is highly thermally stable and porous, rendering large surface area and rich surface chemistry promising for catalytic applications. Aqueous solutions of metal salts were used as the precursors of the nanoparticles, and added in an aqueous dispersion of synthetic clay, laponite, in which the clay exists in exfoliated silicate sheets. Acid leaching of the clay sheets occurs in the reaction due to the strong acidity of the metal salt solution. Meanwhile, the metal hydrate ions polymerise because of the high pH of the clay dispersion and condense on the leached silicates. This mechanism is distinctly different from conventional pillaring process. The nanocomposites of various oxides and binary oxides were synthesised. By introducing polyethylene oxide surfactants, we obtained mesoporous nanocomposites with very large surface areas (400-900 m2/g) and porosity. These nanocomposites are superior catalysts or catalyst supports over of microporous pillared clays [1-3] due to their structure and surface properties.
Novel Synthesis of Aluminium Oxide Nanofibers
Authors: Zhu Huai. Y. , Lu Gao. Q.
Published: April 2011

This report presents a novel synthesis method of alumina nanofibers at moderate conditions in aqueous systems through a surfactant-directed crystal growth process. In the presence of polyethylene oxide (PEO) surfactants, boehmite nanofibers of about 3 nm thick and 30-60 nm long formed from aluminium hydrate colloids. During the subsequent heating, the surfactant was evaporated and boehmite nanofibers were converted into γ-alumina nanofibers. The function of the PEO surfactant and the formation mechanism of the nanofibers are discussed. Alumina nanofibers are an ideal structural reinforcement for various nanocomposite materials. They are potential adsorbents with high adsorption capacity. Furthermore, their unique structure exhibits strong resistance to heating at high temperatures. The BET surface area of a typical sample after heating at 1200°C is as high as 68 m2/g. This makes the material very promising as excellent substrates for catalysts of high thermal stability.
Investigating Catalytic Properties of Composite Nanoparticle Assemblies
Authors: Maye M.M. , Luo J. , Lou Y. , Ly N. K. , Chan W.-B. , Phillip E. , Hepel M. , Zhong C.J.
Published: April 2011

We present herein recent findings of an investigation of catalyst assembly and activation using metallic nanoparticles encapsulated with organic monolayers. Gold nanocrystals (2∼5 nm) encapsulated with thiolate monolayers assembled on electrode surfaces, were found to be catalytically active towards electrooxidation of CO and MeOH upon activation. The activation involved partial removal of the encapsulating thiolates and the formation of surface oxygenated species. A polymeric film was also used as a substrate for the assembly of the nanoparticle catalysts. When the polymer matrix was doped with small amounts of Pt, a remarkable catalytic activity was observed. These catalysts were characterized utilizing cyclic voltammetry and atomic force microscopy.
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

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 Pt 2+ 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.
Intercalative Route to Heterostructured Nanohybirds
Authors: Choy Jin-Ho
Published: April 2011

We have successfully synthesized organic-inorganic and bio-inorganic nanohybrids by applying an intercalation technique systematically to Bi-based cuprate superconductors, Bi2Sr2Cam-1CumOy(m = 1, 2, and 3; BSCCO), and to layered double hydroxides(LDHs), those which are of high importance in terms of basic understanding of intercalation reactions and of their practical applications. The organic-inorganic hybrids were achieved via intercalative complexation of iodine intercalated BSCOO with organic salt of Py-CnH2n+1I (Py = pyridine). The high-Tcsuperconducting intercalate with its remarkable lattice expansion can be applied as a precursor for superconducting colloids when dispersed in an appropriate solvent. We were also able to demonstrate that the biomolecules stabilized in the interlayer space of LDH retain their chemical and biological integrity. If necessary, LDH, as a reservoir, can be intentionally removed by dissolving it in an acidic media or interlayer biomolecules in LDH can be released via ion-exchange reaction in electrolyte. It is, therefore, concluded that the inorganic LDH can play a role as a good host lattice for gene reservoir or carrier.
Soft reverse current-voltage characteristics in V2O5 nanofiber junctions
Authors: Kim Gyu-Tae , Muster Jörg , Burghard Marko , Roth Siegmar
Published: April 2011

V2O5 nanofibers showed the rectifying current-voltage characteristics under an asymmetric contact configuration at room temperature, indicating the formation of a Schottky diode. The ideality factors as a Schottky diode were estimated to be 6.1 at the forward bias and 1.4 at the reverse bias. The larger current at the reverse bias defined by the negative voltage at the metal electrode may originate from the contribution of the tunneling via field emission or thermionic field emission. The ultimate geometric size of nanofibers enhances the influence of the tunneling mechanism and modifies the nano-scale Schottky diode, requiring more understanding in designing the nano-scale electronic devices with the metal contacts.
Growth of Solid and Hollow Nanowhiskers from Nanoscale Powders
Authors: Malkhasyan R.T. , Karakhanyan R.K. , Nazaryan M.N.
Published: April 2011

The fast mass growth of solid and hollow nanowhiskers of MoO3 and WO3 is obtained owing to the heating of the nanoscale powders of these materials by means of electron beam. Based on our transmission electron microscopic observation the growth mechanism of the MoO3 and WO3 nanowhiskers is proposed.
The Generation of a Carbon Nanotube- Cyclodextrin Complex
Authors: Farrell G.F. , Chambers G. , Dalton A.B , Cummins E. , McNamara M. , Baughman R.H. , Panhuis M. in het , Byrne H.J.
Published: April 2011

In this study the intermolecular interactions of small diameter (∼0.7nm) carbon nanotubes and γ-cyclodextrin were examined. Four samples of γ cyclodextrin and HiPco carbon nanotubes were prepared. The first, by grinding the tubes and the cyclodextrin (1:30 ratio) together in a dry mixture, the second was prepared in a similar fashion but was ground in the presence of water (1ml). Finally an aqueous solution of γ-cyclodextrin (0.3M) and HiPco carbon nanotubes (5mg) was prepared by refluxing for ∼100 hours, forming a pale yellow solution from which a number of crystals were produced, both the solution and the recrystallised material were analysed. The samples were analysed using UV-Vis-NIR and Raman spectroscopy. The results presented are the first spectroscopic evidence of an intermolecular interaction between γ-cyclodextrin and single wall nanotubes.
Self-Assembly of Metal Nanoclusters in Block Co-Polymers
Authors: Tadd Erica H. , Bradley John , Goldberg Eugene P. , Tannenbaum Rina
Published: April 2011

This paper describes the formation of cobalt and iron metal nanoclusters in various polymeric domains. The size of the particles, their size distribution and their geometry is controlled by the extent of the interfacial interactions between the polymeric phase and the growing metal fragments. Iron oxide particles are shown to exhibit various geometries as a function of the polymer medium and the temperature at which they are formed. The selective phase separation and particle confinement of cobalt clusters in the presence of PS25300-b-PMMA25900 block co-polymer was achieved due to the different reactivities of the functional groups in the blocks towards the metal fragments. Transmission electron micrographs showed that cobalt clusters aggregated primarily in the poly(methyl methacrylate) block, while no cobalt nanoclusters were observed in the polystyrene block, thus creating a patterned distribution that coincided with the morphology of the block copolymer.
Multi-functionalization Of Silicon By Nanoparticles Through “Plug and Play” Approach
Authors: Prabhakaran K. , Shafi K.V.P.M. , Ulman A. , Ogino T.
Published: April 2011

In this paper, we demonstrate a “Plug and Play” approach, whereby externally synthesized nanoparticles of desired functions and size are incorporated into the semiconductor, followed by the manipulation of surface chemical bonds in order to achieve multiple functionality. Sonochemically synthesised Fe2O3 nanoparticles were introduced onto device quality Si wafers. On annealing the particle-treated Si wafer in ultra high vacuum, oxygen changes the bonding partner from Fe to Si and desorb as SiO at ∼ 760°C, leading to the formation of uniform sized Fe nanoparticles ( size ∼6-8 nm) on the surface and the sample shows ferromagnetic behaviour. More importantly, the particle treated Si exhibits light emission at wavelengths 1.57, 1.61 and 1.65 microns (full width at half maximum ∼ 20 meV). Emission in this wavelength range is crucial for optical communications and is highly desired from a Si based material. Further, oxidation of this material leads to the formation of a selective capping layer of SiO2. Thus, by manipulating the surface chemical bonds, we are able to introduce optical, magnetic, metallic and insulating functions to Si. Additionally, the particles exhibit self-assembly on a patterned Si surface. We believe that this approach is universal and the material developed here is compatible with the planar Si technology, bringing us closer to realization of Si based monolithic electronics.
Solvothermal Synthesis Of Electrochemically Active Nanocrystalline Li-Ti-O Spinel
Authors: Fattakhova Dina , Krtil Petr
Published: April 2011

Nanocrystalline 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

We 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

This 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

Vanadium 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

Nanocomposite 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

Octanethiol-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

The 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

The 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

Sodium 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

The 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

The 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

We 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

Two 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

The 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

Semiconductor 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

A 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

Highly 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

To 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

Carbon 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

We 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

The 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.