bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Conductivity of Ionic and Electronic Mixture
Authors: Choi Gyeong Man , Kim Joon Hee , Park Young Min
Published: April 2011

Mixed ionic-electronic conductors (MIECs) which have both ionic and electronic species as charge carriers have a wide range of applications, such as electrodes in fuel cells, electrocatalytic reactors, and gas separating membranes. They may have either electronic or ionic species as the majority charge carriers. In addition to the single-phase mixed conductors, they may be fabricated by mixing two different phases of materials. Although these composites have been less studied than the single phase MIECs, the combined properties are often superior to single phase MIECs, and properties not seen in an individual phase may appear in the composite phase.

YSZ-based composite systems were chosen to test the effect of transition-metal-oxide (TMO) addition on the electronic conductivity of composite. To induce mixed conductivity, electronic-conducting TMOs such as NiO and Mn2O3 were added into YSZ above the solubility limit. While the solid solubility of NiO in YSZ is limited that of Mn2O3 is large.

In this work, mixed conducting yttria (8 mol%) stabilized zirconia (YSZ) - TMO composites were prepared in full composition range and the electrical conductivity of the composites was measured by 4-probe d.c. conductivity. Electromotive force (emf) measurements of the galvanic cell, current-voltage (I-V) measurements in ion blocking condition and the oxygen-partial-pressure dependent conductivity have been used to determine the contribution of the ionic and electronic charge carriers on the conductivity. Thus the composition-dependent electrical properties were used to explain the percolation behavior of electronic charge carriers in ionic matrix.

Although the total conductivity of dense YSZ-TMO composite was variable with TMO content, the partial-electronic conductivity increased and the ionic conductivity decreased. The composition-dependent conductivity was discussed.
Combinatorial Synthesis and Characterization of Zinc-Tin-Oxide Transparent Conductors
Authors: Perkins J.D. , Cueto J.A. del , Alleman J.L. , Warmsingh C. , Keyes B.M. , Gedvilas L.M. , Parilla P.A. , To B. , Readey D.W. , Ginley D.S.
Published: April 2011

In this work, we discuss the combinatorial deposition and analysis of transparent conducting oxides along the ZnO-SnO2 composition tie line. Libraries were deposited by co-sputtering from ZnO and Sn-metal targets. The production and analysis of Zn-Sn-O libraries has already produced significant results, confirming the properties of the 2:1 (Zn2SnO4) region and revealing a second region of interest, the 1:1(ZnSnO3) composition. Subsequent film growth of these stochiometries by pulsed laser deposition has confirmed the potential for both of these stochiometries. Work is currently underway to optimize both Zn2SnO4 and ZnSnO3. Planned future work includes a combinatorial investigation of ternary metal systems such as Zn-In-Sn-O.
Combinatorial Synthesis Approach for Optimizing Oxide/Si Interfaces for the Future Ulsi
Authors: Chikyow T. , Ahmet P. , Naruke T. , Nakajima K. , Okazaki N. , Hasegawa K. , Minami H. , Itaka K. , Koida T. , Song J.H. , Yoshimoto M. , Hasegawa T. , Kawasaki M. , Koinima H.
Published: April 2011

A combinatorial material synthesis with temperature gradient heating system was employed to optimizing growth parameters for oxide growth on Si substrate. From the obtained results, it was found the dielectric property depends on the growth temperature as well as the composition. The interface structures were investigated by high resolution electron microscopy with a series of specimens fabricated by micro sampling method. The results showed that amorphous oxide region and SiO2 layer were formed at the interface. It was speculated that the amorphous oxide region contributed to the reduction of the dielectric property. To avoid the amorphous and SiO2 formation at the oxide/Si interface, a few kinds of intermediate layers were inserted and tested to find the possibility of abrupt interface formation.
On the Implementation of Neural Network Concept to Optimize Thermal Spray Deposition Process
Authors: Guessasma Sofiane , Montavon Ghislain , Coddet Christian
Published: April 2011

Numerous processing parameters, up to fifty, characterize the plasma spray deposition process. A better quality control of the resulting deposits induces a better understanding of their effects on coating formation mechanisms. Numerical models can help to provide such an understanding. From a mathematical point of view, d.c. plasma spray deposition process is assimilated to a nonlinear problem in regards to its variables (operating parameters, environment, etc.). This paper develops a global approach based on an implicit describing of the mechanisms implementing Artificial Neural Networks (ANNs). The global concept and the protocols to implement are presented and developed for an example related to d.c. plasma spray process.
Designing Conducting Polymers with Genetic Algorithms
Authors: Giro R. , Cyrillo M. , Galvão D.S.
Published: April 2011

We have developed a new methodology to design conducting polymers with pre-specified properties using genetic algorithms (GAs). The methodology combines GAs with the Negative Factor Counting (NFC) technique. NFC is a powerful technique to obtain the eigenvalues of large matrices without direct diagonalization.We present the results for a case study of polyanilines, one of the most important families of conducting polymers. The methodology proved to be able of generating automatic solutions for the problem of determining the optimum relative concentration for binary and ternary disordered polyaniline alloys exhibiting metallic properties. The methodology is completely general and can be used to design new classes of materials.
Molecular Dynamics Simulations of Reactive Wetting
Authors: Webb Edmund B. , Grest Gary S.
Published: April 2011

The wetting and spreading of liquid Ag drops on Cu (001) surfaces are studied with molecular dynamics simulations. As the liquid Ag drop spreads on the Cu surface, reactive wetting occurs in that a Ag/Cu alloy is formed. The results for the reactive wetting case are compared to a frozen substrate for which there is no alloying. At the highest temperature studied, T = 1300 K, the radius of the drop spreads faster than for the frozen substrate, indicating the driving force for spreading is greater when the liquid and solid mix. Lowering temperature in reactive systems results in behavior more similar to non-reactive systems due to suppressed mixing.
Growth of Nanosize and Colloid Particles by Controlled Addition of Singlets
Authors: Privman Vladimir
Published: April 2011

We outline a theoretical framework for estimating the evolution of the particle size distribution in colloid and nanoparticle synthesis, when the primary growth mode is by externally controlled addition of singlet building blocks. The master equations, analyzed in the leading “non-diffusive” expansion approximation, are reduced to a set of easily numerically programmable relations that yield information on the time evolution of the particle size distribution.
Fibers of Bamboo and Hem Palm Tree
Authors: Amada Shigeyasu
Published: April 2011

Bamboo is a typical composite material which is axially reinforced by very strong fibers. So that, the fibers play an important role for the bamboo structure. The elastic properties of the bamboo culm have been measured only by tensile test so far, which needs a large specimen. Recently ultra-sonic technique, which has a simple procedure and uses a small specimen, has been applied to woods as well as metals. This report reviews about the elastic properties of bamboo and Hemp palm fibers. The Young's modulus and Poisson's ratio of the bamboo fibers are measured by ultra-sonic method with a transmitting wave. On the other hand, the strength of the bamboo and Hemp palm fibers are measured by the tensile tests. Using the volume fraction of fibers in the specimen and mixture principle, the Young's modulus and strength of the fibers and parenchyma were obtained. The fiber has a high strength up to 1GPa and an strong anisotropic property because its axial Young's modulus has 7 times higher than the one in the transverse direction.
Production and Characterization of Yarns and Fabrics Utilizing Turkey Feather Fibers
Authors: Evazynajad Alimohammad , Kar Adnan , Veluswamy Sathpurushan , McBride Holly , George Brian R.
Published: April 2011

Turkey feather fibers were characterized and then converted into products such as yarn and nonwoven fabrics for a study into the feasibility of their use as textile products. Yarn containing blends of nylon and up to thirty percent turkey feather fibers were spun by combining novel techniques with commercial yarn spinning machinery. These yarns were tested for determination of their mechanical properties. As the percentage of turkey feather fibers increased, the tenacity and elongation of the yarns decreased while the modulus increased. These yarns were knitted into fabrics to determine their insulating properties. As the percentage of turkey feather fibers increased the insulating capabilities of the fabrics also increased. Recent research has focused on producing nonwoven fabrics containing turkey feather fibers utilizing various production methods for use as erosion control fabrics.
Electrostatic Synthesis and Characterization of Pb(ZrxTi1-x)O3 Micro/nano-fibers
Authors: Wang Yu , Serrano Santiago , Santiago-Aviles Jorge J.
Published: April 2011

Pb(Zr0.48Ti0.52)O3 (PZT) micro/nano-fibers and mats were synthesized from alkoxides using electrostatic deposition. The PZT micro/nano-fibers precursor, a mixture of zirconium npropoxide, titanium isopropoxide, and lead 2-ethylhexanoate, was deposited under the following conditions: tip-screen distance=15cm, voltage drop between tip and screen of 15kV. The deposited fibers and mats samples were sintered for half an hour at 400, 500, 600, 700, and 800°C, respectively. Sintered mats were characterized using x-ray diffraction (XRD), sintered fibers were characterized using optical microscope, scanning electron microscopes (SEM), Raman microscope, and scanning probe microscope (SPM). SEM revealed that micro/nano-fibers have diameters varying from a fraction of a micron to around 10 micrometer. XRD and Raman spectra indicated that the precursors begin to transform into intermediate phase Pb2Ti2O6 at 400°C, whose transformation into the perovskite phase starts at 600°C and ends at 800°C. Scanning probes microscope (SPM), operated in voltage-modulated dynamic contact mode, revealed the spontaneous polarization domains, with diameters ranging from 0.1 to 0.5 micron, in microfibers, confirming their piezoelectricity.
Acoustic Imaging of Microstructures of Carbon Fiber-Reinforced Composite Laminates
Authors: Liu Songping , Levin Vadim M. , Guo Enming
Published: April 2011

The properties and homogeneity of a composite laminate are strongly dependent on structures and microstructures in it. The investigations have shown that the microstructures of carbon fiber-reinforced polymer composite laminates can be visualized by means of acoustic imaging techniques. The frequency of ultrasonic wave to be used is up to 50MHz. The composite laminates to be investigated include unidirectional carbon fiber-reinforced polymer composite laminates, bi-directional carbon fiber-reinforced polymer composite laminates and carbon fiber woven composite laminates. Very useful quantitative information about inside structures of the composites can be visualized in plan-section of the laminates in the depth directions by ultrasonic T-scan imaging technique. Typical results have been represented in this article.
Lenzing Lyocell – a versatile fiber
Authors: Eichinger D. , Firgo H. , Rohrer Ch.
Published: April 2011

Cellulosics have a very balanced set of general features, with its unique specific control of moisture resulting in widely accepted physiological benefits and wearing comfort. This gives interesting future prospects for the man-made cellulosics Viscose, Modal and Lyocell by Lenzing AG. The fibres produced cover a wide range of nowadays possibilities from the viscose and Lyocell process, covering textile, non woven, technical or medical application. For a brief introduction into the different types some of the main properties are given in table 1 compared with other fibres.
Biopolymer-silica Hybrid Aerogels Containing Transition Metal Species; Structure, Properties, and Reactions
Authors: Hu Xiangjun , Ji Shuang , Risen William M.
Published: April 2011

Novel transition-metal containing hybrid biopolymer-silica aerogels have been synthesized as transparent monolithic structures. The compositions include Ru(III), Rh(III), Co(II), and Pd(II) species, silica and chitosan, and amine-group-containing biopolymer derived from chitin. Due to its aqueous solubility and hydrogen bonding properties, chitosan was homogeneously incorporated into the silica network. These aerogels have densities in the range of 0.25-0.30 g/cm3, BET surface areas in the range of 600-975 m2/g, and refractive indexes below 1.17 (at 632.8 nm). Infrared spectroscopy shows that chitosan is effectively introduced into the silica aerogels, and the transition metal ions can coordinate with the amine sites on chitosan. This combines the metal-ion interaction of chitosan with that of silica aerogels. Transmission electronic microscopy indicates that the particle sizes of silica are about 2 nm. Small angle neutron scattering (SANS) has been used to study the microstructure of these aerogels. A new Small-Particle Mass-Fractal model scattering function, derived from the Teixeira Mass-Fractal model scattering function, was used to fit the SANS data. It was found that chitosan helps to form an open aerogel structure. It supports a structural model in which there are primary particles that connect with each other closely to form clusters, and these clusters serve as a secondary structural unit to form the chitosan-reinforced aerogel network. It also indicates that chitosan reinforces the interparticle connections. The local environments, structures and chemistries of the transition metal ions have been explored. Of special interest in this regard are the magnetic properties of the Ru(III) containing materials, which are consistent with anti-ferromagnetic coupling, and the reactions of the Rh(III), Ru(III), and Pd(II) species with small gaseous molecules.
Reduction of Moisture Sensitivity in Natural Fibres
Authors: Pott Gerard T.
Published: April 2011

When natural fibres are applied as reinforcement in polymer composites the moisture sensitivity, causing fibre swell and ultimately rotting through fungi attack, can be a very serious problem. A number of methods have been developed dealing with this problem that change the chemical and / or physical composition of the fibre, resulting in reduced moisture sensitivity. To this category belongacetylationandhydrothermaltreatment. For acetylation, acetic anhydride is used as a chemical that reacts with reactive OH-groups of the lignocellulose material, increasing hydrophobicity. In hydrothermal treatment no chemicals are used, only water and energy.

The main focus of this paper is on hydrothermal treatment, the Duralin® process in particular, of bast fibres such as flax, jute and hemp. Acetylation is reviewed briefly. A survey is given of the structure and composition of bast fibres and the moisture adsorption and desorption mechanisms in these fibres.

The Duralin® process involves three steps, hydrothermolysis, drying and curing. The raw material for the Duralin® process applied to flax is green rippled flax straw. This eliminates the need for the traditional dew-retting, a risky process where the freshly harvested flax stems lay on the field for about four weeks. The Duralin® process reduces moisture absorption and biological degradation, the fibre yield is higher than after dew-retting and the shives can be used as a filler material in polymers and for making a water proof particle board. The main causes for reduced water uptake after Duralin treatment will be reviewed.

Duralin® fibres have equal or higher tensile strength and higher flexural modulus than fibres extracted from dew-retted flax. Compounds reinforced with these fibres have apart from decreased moisture sensitivity a better mechanical performance. Both the amount and the release rate of decomposition products resulting from compounding with polypropylene are significantly less for Duralin® fibres than for dew-retted or green fibres. Duralin® fibres are on a weight basis competitive with glass fibres.
Recent Advances in Oxide Glass Fiber Science
Authors: Lawton Ernest L. , Wallenberger Frederick T. , Li Hong
Published: April 2011

The predominate substrate for multilayer printed wiring boards is laminate constructed from epoxy resin reinforced with fiber glass fabrics. This combination of materials dominates the segment of the electronics market where dimensional stability of the substrate is critical. The rapid development of high speed digital and analog electronic systems has challenged the predominance of fiber glass as the reinforcement of choice. As systems move to the GHz frequency range, there is a need for lower dielectric constant of the substrate to insure integrity and speed of signals. A lower dissipation factor of the substrate is desired for the wireless communication applications of printed wiring boards. A review is presented of materials competing as substrates for the high speed application of the printed wiring board market.
Continuous Carbon Nanofibers For Nanofiber Composites
Authors: Dzenis Yuris , Wen Yongkui
Published: April 2011

Continuous carbon nanofibers were manufactured using electrospinning technique. The as-spun polyacrylonitrile (PAN) nanofibers were stabilized and carbonized to convert them into carbon nanofibers. The diameters of typical carbon nanofibers were in the range from 100 -500 nanometers. Compared to the vapor grown carbon nanofibers, the electronspun carbon nanofibers were continuous, uniform in diameter, and solid. The electrospun nanofiber samples did not require purification. The carbon nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Electron and X-ray diffraction patterns were obtained and analyzed. Nanocomposites of epoxy resin reinforced with as-spun PAN and carbon nanofibers were fabricated and analyzed. The results showed good potential of continuous carbon nanofibers for nanocomposite and other applications.
Carbon Nanofiber Treatment Effects On Composite Properties
Authors: Burton David J. , Glasgow D. Gerald , Kwag Choongyong , Lake Max L.
Published: April 2011

Carbon nanofibers (CNF) are vapor grown carbon fibers grown catalytically from gaseous hydrocarbons using metallic catalyst particles. While this type of carbon fiber has been known for many years, only recently have composite properties been studied. Rules for composite synthesis teach that composite properties depend on several key parameters, including fiber-matrix interphase and fiber aspect ratio. Good adhesion between these fibers and matrix resins is essential for the performance of CNF based composites, so the mechanical properties of composites are strongly influenced by fiber surface morphology and chemistry. This work examines the fiber-matrix adhesion problem as influenced by CNF fiber surface area and surface energy, and the impact of aspect ratio on composite electrical properties.
Design of Sandwich Composites with Multi-Functional Facesheets
Authors: Vaidya Uday K. , Pillay Selvum , Ricks Helena , Bartus Shane , Ulven Chad , Mathew Biju
Published: April 2011

Sandwich composites find increasing use as flexural load bearing lightweight sub-elements in air / space vehicles, rail / ground transportation, marine and sporting goods. The core materials in these applications is usually balsa, foam or honeycombs, while laminated carbon or glass are used as facesheets. A limitation of traditional sandwich configurations is that the space in the core becomes inaccessible once the facesheets are bonded in place. Significant multi-functional benefits can be obtained by making either the facesheets or the core, space accessible. Multi-functionality is generally referred to as value added to the structure that enhances functions beyond traditional load bearing. Such functions may include sound / vibration damping, ability to route wires or embed sensors. The present work considers traditional core materials of nomex and aluminum honeycombs that possess functional space accessible facesheets, and their low velocity impact (LVI) response.
Spectroscopic Elucidation of Lanthanide Cation Dissolution Mechanism in Borosilicate Glass
Authors: Li Hong , Wang Zheming , Li Liyu , Strachan Denis M. , Su Yali. , Joly A.G.
Published: April 2011

Oxides of lanthanide dissolution in a Na2O-Al2O3-B2O3-SiO2 glass using Gd as a probe was studied in detail using Raman, fluorescence, and phonon sideband (PSB) spectroscopic techniques. A mechanism of Gd cation dissolution, via partitioning, in the borate-rich and silicate-rich environments was confirmed by examining characteristics of the Raman band evolution, fluorescence emission and lifetime, and PSBs. The study concluded that i) Gd(III) cations in the borate-rich environment resembles Gd-metaborate local structure, i.e., 1BO4:1Gd:2BO3, ii) Gd cations partitioning in the borate-rich environment at low Gd2O3 concentration, [Gd2O3] -1/3[B2O3] < 0, and iii) excess Gd(III) cations, [Gd2O3]–1/3[B2O3], in the silicate-rich environment at high Gd2O3 concentration, [Gd2O3]–1/3[B2O3]>0.
Optimization of the In-Situ Al-Si Base Functionally Graded Material Fabricated by Centrifugal Casting
Authors: Oya-Seimiya Yoshihiro , Shinoda Tetsumori , Watanabe Yoshimi
Published: April 2011

The fabricating conditions for the in-situ Al-Si base composite by the centrifugal casting method (CCM) have been examined. The crystallized Si particles with a lower density distribute in a gradient fashion as densely on the inner and thinly on the outer side of the wall of the cylindrical CCM-composite. Synthetically, the 25 mol% Si composite is recommended for the application like the engine liner.
Anhydride/Epoxy Functionalized Blends: Mechanical, Rheological and Thermal Properties
Authors: Bayram Goknur , Yilmazer Ulku
Published: April 2011

Blends of styrene-maleic anhydride (SMAH) and polyethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) were produced in a batch mixer and in a corotating twin screw extruder. E-MA-GMA concentration was varied from 0 % to 50 %. Batch mixing indicated that the blend system was reactive. Extruded blends were characterized in terms of rheological, thermal and mechanical properties, and their morphology was observed. Rheological properties such as the storage modulus, loss modulus and complex viscosity exhibited maxima at 25 % EMA-GMA content. The blends had fine morphology as observed by scanning electron microscopy. Thermal properties were not significantly affected by the change in epoxy concentration. As E-MA-GMA concentration increased, tensile strength and modulus of elasticity decreased, but percent strain at break increased. These observations could be explained in terms of the chain extension / branching reactions that occurred in mixing the blends.
Processing, Dynamic Studies and Properties of Exfoliated Aerospace Epoxy-Organoclay Nanocomposites
Authors: Chen Chenggang , Curliss David
Published: April 2011

Epoxy nanocomposites were prepared from the montmorillonite after organic treatment with a high Tg epoxy resin (Shell Epon 862 and curing agent W). Investigation of the rheological characteristics showed that the addition of clay to the resin did not significantly alter the viscosity or cure kinetics and that the modified resin would still be suitable for liquid composite molding techniques such as resin transfer molding. DSC was performed to study the kinetics of the curing reactions in the modified resin. An in situ small-angle x-ray scattering (SAXS) experiment was used to try to understand the structural development during cure. Based on the in situ SAXS data, structural changes were monitored in real time during cure and analyzed. Results from wide-angle x-ray diffraction, SAXS, and transmission electron microscopy of the polymer-silicate nanocomposites were used to characterize the morphology of the layered silicate in the epoxy resin matrix. The glassy and rubbery moduli of the polymer-silicate nanocomposites were found to be greater than the unmodified resin due to the high aspect ratio and high stiffness of the layered silicate filler. The solvent absorption in methanol was also slower for the polymer-silicate nanocomposites.
Study of NiFe/SiO2 Nanocomposites
Authors: Hui S. , Zhang Y.D. , Xiao T. D. , Wu Mingzhong , Ge Shihui , Hines W. A. , Budnick J. I. , Yacaman M. J. , Troiani H. E.
Published: April 2011

(Ni75Fe25)v/(SiO2)1-v nanocomposites with v =0.5, 0.7, and 1.0, where 75 denotes the atomic percent of Ni in the Ni-Fe alloy phase and v denotes the volume fraction of the magnetic constituent in the composite, were synthesized using a wet chemical approach. The x-ray diffraction and TEM experiments show that the synthetic NiFe/SiO2 is a two-phase composite system in that an amorphous insulating SiO2 layer coats each Ni-Fe particle. The Ni-Fe particle is in a fcc Ni-Fe alloy state. Its size can be controlled over a rather large range between 5 nm to 70 nm by adjusting the reaction parameters. Particular attention was paid to reduce the chemical reaction temperature so as to insure the smallness of the particle size. Meanwhile, measurements of the saturation magnetization indicated that the higher the heat treatment temperature, the more complete the chemical reaction to form the Ni-Fe alloys from precursor materials.
Studies of Intersubband Transitions in Arrays of Bi Nanowire Samples Using Optical Transmission
Authors: Black M. R. , Maskaly K. R. , Rabin O. , Lin Y. M. , Cronin S. B. , Padi M. , Fink Y. , Dresselhaus M. S.
Published: April 2011

This paper reports the fabrication of large diameter pores (> 150 nm) in anodic aumina that can be used to create wire arrays with significant surface effects, but without significant quantum confinement. These wires, therefore, allow us to distinguish between optica absorption spectra features originating from quantum effects and those from surface effects. The paper presents techniques towards fabricating these bismuth wire arrays, and presents optical absorption data from two bismuth nanowire arrays in the semimeta-semiconductor transition diameter regime. The results from previous publications are summarized and future directions are outlines.
Insertion of Inorganic-Biomolecular Nanohybrid into Eucaryotic Cell
Authors: Kwak Seo-Young , Hwang Sung-Ho , Jeong Yong-Joo , Park Jong-Sang , Choy Jin-Ho
Published: April 2011

It has been clearly demonstrated that ATP could be intercalated into inorganic layered double hydroxide (LDH), giving rise to a biomolecular-inorganic nanohybrid with preserving its physico-chemical and biological integrity. It shows a remarkable transfer efficiency of ATP into target cells byalleviating anelectrical repulsion at the cell walls due to the neutralization of negative charge of phosphates by positive hydroxide layers. From cellular uptake experiment with laser scanning confocal fluorescence microscopy, it is revealed that the FITC-LDH hybrid is effectively transferred into 293 cells. Such an unique feature of biomolecule-LDH hybrid will open a new field of reserving and delivering genes, drugs and other functional biomolecules.
Catalyst-free Growth of Large Scale Ga2O3 Nanowires
Authors: Chang Ko-wei , Liu Sai-chang , Chen Liang-Yih , Hong Franklin Chau-Nan , Wu Jih-Jen
Published: April 2011

Large scale of straight Ga2O3 nanowires is grown on a fused silica substrate by a simple catalyst-free CVD method using Ga metal and N2 / H2O reactants. The Ga2O3 nanowires with diameters ranging from 60 to 150 nm can be as long as several micrometers. XRD and TEM analyses indicate that the Ga2O3 nanowires exhibit a monoclinic structure. PL characteristic of the Ga2O3 nanowires shows a UV emission of 375 nm at room temperature.
Stress and Hardness of CrNx films
Authors: Janssen G.C.A.M. , Kamminga J.-D. , Sloof W.G.M.
Published: April 2011

Chromium nitride films CrNx with x ranging form 0 to 1 were deposited by reactive PVD. Both stress and hardness in the films are a function of the composition. The growth stress and hardness for the majority of the films can be related through the Hall Petch relation. It is shown that the hardest films fall outside this relation. It is also shown that the hardest films are nanocrystalline. It is argued that the hardness of these films is a consequence of the nanocrystallinity of these films.
Nanostructured NiFe2O4 Soft Magnetic Ferrite
Authors: Zhang Zongtao , Zhang Y. D. , Xiao T. D. , Ge Shihui , Wu Mingzhong , Hines W. A. , Budnick J. I. , Gromek J. M. , Yacaman M. J. , Troiani H. E.
Published: April 2011

NiFe2O4 is an important high frequency soft magnetic material due to its ultra high resistivity; however, its initial permeability is rather low. Conventional magnetic ferrites are manufactured through ceramic processing. In an effort to explore innovative approaches for fabricating ferrite materials with improved performance, a study of fabricating nanostructured NiFe2O4 using wet chemical approaches has been carried out. The synthetic NiFe2O4 precursor was synthesized by a citrate reaction method followed by calcinating at various temperatures. Systematic studies concerning the crystallographic structure, the nanostructure and morphology of the particle, the phase homogeneity, the conditions for chemical reaction completion, and the magnetic properties have been carried out using x-ray diffraction, transmission electron microscopy, and magnetic measurements. The results show that by using a citrate reaction approach, pure phase and stoichiometric NiFe2O4 can be fabricated easily, and the particle size can be controlled on a nanometer scale, even at high calcination temperatures. In addition, a comparative study of the NiFe2O4 fabricated by conventional ceramic processing and this new citrate processing will be presented.
Dynamic Fracture Mechanisms in Nanostructured and Amorphous Silica Glasses Million-Atom Molecular Dynamics Simulations
Authors: Brutzel Laurent Van , Rountree Cindy L. , Kalia Rajiv K. , Nakano Aiichiro , Vashishta Priya
Published: April 2011

Parallel molecular dynamics simulations are performed to investigate dynamic fracture in bulk and nanostructured silica glasses at room temperature and 1000 K. In bulk silica the crack front develops multiple branches and nanoscale pores open up ahead of the crack tip. Pores coalesce and then they merge with the advancing crack-front to cause cleavage fracture. The calculated fracture toughness is in good agreement with experiments. In nanostrucutred silica the crack-front meanders along intercluster boundaries, merging with nanoscale pores in these regions to cause intergranular fracture. The failure strain in nanostructured silica is significantly larger than in the bulk systems.
Sol-Gel Synthesis and Characterization of Neodymium-Ion Doped Nanostructured Titania Thin Films
Authors: Burns Andrew , Li W. , Baker C. , Shah S.I.
Published: April 2011

Nd doped TiO2 nanostructured thin films were prepared by sol-gel technique on quartz and Si substrates using TiCl4 precursor. As-deposited amorphous films were annealed to form anatase phase in the thin films. The film grain size increased with annealing temperature. Above 800°C, rutile began to segregate and the grain size decreased slightly.

The photodegradation of 2-chlorophenol (2-CP) was studied. Doping TiO2 with Nd+3 reduced the photodegradation time. The difference in the ionic radii of Nd+3 and Ti+4 and the oxygen affinities of Nd and Ti were responsible for this effect. These differences help promote electron trapping, thereby increasing the lifetime of the holes which are responsible for the oxidation of 2-CP.
Insight into the Formation of Ultrafine Nanostructures in Bulk Amorphous Zr54.5 Ti7.5Al10Cu20Ni8
Authors: Heinemann André , Hermann Helmut , Wiedenmann Albrecht , Mattern Norbert , Kühn Uta , Bauer Hans-Dietrich , Eckert Jürgen
Published: April 2011

Bulk amorphous Zr54.5 Ti7.5Al10Cu20Ni8 is investigated by means of smal-angle neutron scattering (SANS), differential-scanning calorimetry (DSC), high-resolution electron microscopy (HREM) and other methods. The formation of ultrafine nanostructures in the glassy phase is observed and explained by a new model. Structura fluctuations of randomly distributed partialy ordered domains grow during annealing just below the glass transition temperature by local re-ordering. During anneaing the DSC gives evidence for a increasing volume fraction of the localy ordered domains. At high volume fractions of impinging domains a percolation threshold on the interconnected domain boundaries occurs and enhanced diffusion becomes possible. At that stage SANS measurements lead to satistically significant scattering data. The SANS signals are anayzed in terms of a model taking into account spherica particles surrounded by diffusion zones and interparticle interference effects. The mean radius of the nanocrystaline particles is determined to 1 nm and the mean thickness of the depletion zone is 2 nm. The upper limit for the volume fraction after annealing at 653 K for 4hours is about 20 %. Electron microscopy confirms the size and shows that the particle are crystaline.
Orientation of Aromatic Ion Exchange Diamines and the Effect on Melt Viscosity and Thermal Stability of PMR-15/ Silicate Nanocomposites
Authors: Campbell Sandi , Scheiman Daniel
Published: April 2011

Nanocomposites of PMR-15 polyimide and a diamine modified silicate were prepared by addition of the silicate to the PMR-15 resin. The orientation of the ion exchange diamine within the silicate gallery was determined by x-ray diffraction and found to depend on the clay cation exchange capacity. The oligomer melt viscosity exhibited a dependence on the orientation of the diamine in the silicate interlayer, and in some cases, on the length of the diamine. A correlation was observed between the oligomer melt viscosity and the crosslinking enthalpy, where nanocomposites with an increased melt viscosity exhibited a decrease in enthalpy on crosslinking. After crosslinking, those nanocomposites with a high melt viscosity had poorer thermal oxidative stability compared to the less viscous systems. The melt viscosity was tailored by co-exchange of an aromatic diamine and an aliphatic amine into the silicate. Nanocomposites prepared with this silicate exhibited an increase in thermal oxidative stability compared to the neat resin.
Rapid-Solidification Effect on Magnetostriction in Iron-based Ferromagnetic Shape Memory Alloy
Authors: Furuya Yasubumi , Kubota Takeshi , Okazaki Teiko , Sato Mitsutaka , Wuttig Manfred
Published: April 2011

Fe-29.6at%Pd ferromagnetic shape memory alloy (FSMA) ribbon formed by rapidly solidified, melt-spinning methods is expected to be useful as a new type of material which shows giant magnetostriction as well as quick response. The giant magnetostriction in the rolling direction depends strongly on applied magnetic-field direction and has a maximum value of 8×10-4 when the field is normal to the surface. This phenomenon is caused by the rearrangements of activated martensitic twin variants. The inverse phase transformation temperatures (As) obtained from Laser micrographs and magnetization vs. temperature curve are ∼307 K and 400∼440 K, respectively. We analyze magnetostriction, magnetic property and crystal structure of Fe-29.6at%Pd bulk sample before rapid solidification and the ribbon sample. From these results, it can be concluded that remarkable anisotropy of giant magnetostriction of ribbon sample is caused by the fine structure formed by the melt-spinning method. It may be possible to apply this method successfully to other FSMA and Ni2MnGa, which is difficult to manufacture owing to its brittleness.
Nanoscale compositional changes along fast ion tracks in equilibrium solid solutions: A computer simulation of ultra-fast solidification and thermomigration
Authors: Lopasso Edmundo M. , Caro Alfredo , Arregui Eduardo Ogando , Caro Magdalena
Published: April 2011

Starting from two equilibrium solid solutions in the Au-Ni system, we analyze the change in composition due to a 400 eV/Å fast ion track simulated by molecular dynamics in the Embedded Atom approximation. We aim at determining the influence of the thermodynamic forces derived from the large thermal gradients and the rapid solidification across the solidus and liquidus on the motion of solute atoms. One dimensional gradients as well as analytic models are used to quantitatively determine the domains of influence of these forces. Evidence shows that the liquidus and solidus equilibrium solidification predicted by the phase diagram is not reached during the track. The solute concentration is mainly determined by the combined diffusion and thermomigration mechanisms in the liquid stage.
Preparation of Optically Transparent Films of Poly(methyl methacrylate) (PMMA) and Montmorillonite
Authors: Vasiliu Elena , Wang Chyi-Shan , Vaia Richard A.
Published: April 2011

Transparent polymeric material with enhanced thermal, mechanical and barrier properties are of special interest for advanced structural, optical and photonic applications. The present paper reports a novel solution processing scheme for fabricating optically transparent polymer nanocomposites involving organophilic layered silicates. It is shown that the nanocomposite material prepared with PMMA and an organically modified montmorrilonite maintains the excellent optical transparency of PMMA. Small-angle x-ray scattering of the polymer nanocomposite material does not show any Bragg's reflection of the organophilic layered silicate. The optical transparency of the nanocomposite material is attributed to a high degree of exfoliation of the montmorrilonite in the polymer matrix.
Characterization of the Morphology of Faceted Particles by Transmission Electron Microscopy
Authors: Turner Shirley , Bright David S.
Published: April 2011

Faceting in a polyhedral rutile particle was modeled from transmission electron microscopy images. A double-tilt, rotate transmission electron microscope (TEM) sample holder was used to manipulate the particle. Using this holder, it was possible to align the c axis of the particle along one of the axes of the sample holder. This alignment allowed images to be obtained of the particle in several orientations around its c axis. Comparison of dimensions and angles obtained to those obtained for hypothetical models of the particle gives information about its likely prismatic and pyramidal faceting. This approach to facet modeling is useful for more complete determination of the faceting in individual euhedral particles using transmission electron microscopy.
Nickel Nanocomposite Thin Films
Authors: Zhou Honghui , Kvit A. , Kumar D. , Narayan J.
Published: April 2011

Nickel was deposited on epitaxial TiN matrix layer grown on Si (100) substrate by pulsed laser deposition process (PLD). Transmission electron microscopy (TEM) study shows that nanoparticles formed are single crystals with two kinds of epitaxial relationship with respect to matrix TiN. One is cube on cube, where (200) Ni // (200) TiN // (200) Si and (022) Ni // (022) TiN // (022) Si. The particles grown in this orientation have a trapezoidal morphology in [011] projection. The other involves a 90 ° rotation with respect to [011] direction of TiN matrix (zone axis), where (022) Ni // (200) TiN // (200) Si and (200) Ni // (022) TiN // (022) Si. The particles grown in this rotated orientation have a triangular morphology in [011] projection and a smaller lattice constant compared with that of pure nickel. The possible mechanism of forming these two epitaxial orientations is discussed. Superconducting quantum interference device (SQUID) magnetometer was used for magnetic measurements. In order to investigate the effect of texturing on magnetic properties of nanoparticles, results were compared with those obtained from Ni nanoparticles grown on amorphous Al2O3 matrix layer in previous research. It was found that both blocking temperature and coercivity of Ni nanoparticles grown on epitaxial TiN matrix are significantly higher than that of Ni grown on amorphous Al2O3. The higher value of coercivity is possibly associated with the stronger tendency of crystallographically oriented particles to retain their magnetic moments in the presence of reversing magnetic field.
Substrate Dependence in the Growth of Three-Dimensional Gold Nanoparticle Superlattices
Authors: Sato S. , Yamamoto N. , Yao H. , Kimura K.
Published: April 2011

Three-dimensional superlattices consisting of gold nanoparticles were grown at air/suspension or suspension/solid interfaces. The growth of superlattices was found to be strongly dependent on substrate materials: Micrometer-sized superlattices were grown at air/suspension interfaces and upon silver substrates, whereas no growth was observed on silicon, silicon oxide, or amorphous carbon substrates. To explain the observed substrate dependence, Lifshitz theory was used to calculate the Hamaker constants between gold nanoparticle assemblies and substrates through the suspension. Van der Waals interactions estimated from this calculation fully explain the experimental results.
The Effect of Interfacial Viscosity on the Kinetics of Formation of Silver Nanoparticles Using Water-in-Oil Microemulsions as Nanoreactors
Authors: Shah D.O. , Bagwe R.P. , Parmar B.S.
Published: April 2011

Silver nanoparticles were prepared by the method of mixing of two microemulsions having similar chemical composition but different reactants in their respective aqueous core. One microemulsion contains silver nitrate in the aqueous core and other contains sodium borohydride. The silver nanoparticles formed were characterized using UV-Visible absorption spectra and TEM micrographs. Effect of chain length of solvent and addition of Arlacel-20 to the AOT/Heptane, AOT/Decane and AOT/Dodecane microemulsion on particle size and absorption spectra of silver nanoparticles was studied. TEM photographs showed agglomerated and bigger particles in case of pure AOT/dodecane whereas addition of Arlacel-20 showed dispersed and smaller particles. Reaction kinetics was observed for silver nanoparticles using UV-visible spectrophotometer. Silver nanoparticles prepared using pure AOT surfactant showed plasmon band (416 nm) immediately after preparation whereas no absorption band of silver nanoparticles was observed for mixed surfactant microemulsion of AOT and Arlacel 20 for few hours indicating the reaction kinetics is slowed down upon addition of Arlacel-20. Growth rate of silver nanoparticles was plotted by monitoring absorption coefficient ratio (ε416/ε475) as a function of time. AOT/heptane system showed slower growth rate as compared to AOT/decane and AOT/dodecane and also larger particle size. Presence of Arlacel-20 significantly decreases the growth rate in all three alkanes and this observation can be explained using the concept of rigidity of surfactant film at the oil/water interface. It is proposed that higher the interfacial viscosity, slower is the coalescence rate of nanodroplets in the microemulsion system, and hence slower the growth rate of particles and smaller is the final particle size.
Size and Composition Effects in the Structure and Properties of Polymer-Protected Bimetallic Particles
Authors: Casanove Marie-José , Lecante Pierre , Fromen Marie-Claire , Respaud Marc , Zitoun David , Pan Cheng , Philippot Karine , Amiens Catherine , Chaudret Bruno , Dassenoy Fabrice
Published: April 2011

We investigate the structural evolution of PtRu and CoRh ultra fine bimetallic particles as a function of their composition in the whole range of stoichiometry. Isolated particles embedded in an organic matrix are synthesized using chemical techniques in mild conditions. Their size, dispersion and structure are analyzed by HRTEM, WAXS and EXAFS techniques. The magnetic behavior of cobalt-based alloys is investigated by SQUID magnetometry. In the PtRu alloys, we demonstrate the role of composition in the structural transition from the face-centered cubic to the hexagonal close packed structure in nanoparticles and detail the mechanism of the transition. We point out the effect of size reduction and core-shell atomic distribution in the structure and the enhanced magnetization in CoRh bimetallic particles.
Ab Initio Molecular Dynamics and Elastic Properties of TiC and TiN Nanoparticles
Authors: Postnikov A. V. , Entel P.
Published: April 2011

The results of first-principles simulations of relaxed ground-state structure and vibrational modes are presented for titanium carbide and titanium nitride clusters of nearly stoichiometric composition and compared to frozen phonon and molecular dynamics calculations for crystalline TiC and TiN. The calculations have been done with the SIESTA method, using norm-conserving pseudopotentials and the basis of strictly localized numerical pseudoatomic orbitals. The dominant vibration mode corresponding to the zone-center TO phonon (14 THz) persists and gets hardened (21 THz) in the small Ti4C4 cluster. The increase of the cluster size to Ti14C13 leads to an enhancement of vibrational density of states in the intermediate range of frequencies, including the phonon band gap of pure crystalline TiC (near 15 THz). Similar trends can be noted for the Ti-N system, with the vibration spectrum slightly scaled upwards but otherwise very close to that of TiC. The clusters studied are yet too small to perform a reliable analysis of acoustic modes.
Controlled and Selective Aggregation of Submicrometer Cu-Crystallites on FIB Sensitized p-Si
Authors: Spiegel Adrian , Schmuki Patrik
Published: April 2011

Electrochemical deposition of metals and alloys onto metallic substrates plays an important role in many modern technologies. Usually, a photolithographic patterning process is used to produce the desired feature on the substrate surface. An alternative method to patterned metal deposition on semiconductors is presented here: it is based on changing the electrochemical properties of the semiconductor by controlled surface defect creation. A focused ion beam (FIB) was used to introduce defects into p-Si, followed by a selective electrochemical reaction to produce metal structures in the sub-micrometer range.

In this work we study the selective deposition behavior of Cu on FIB sensitized surface locations and show that crystallite growth follows a three- dimensional growth law. Crystallites grow very rapidly in a first phase and reach a size of roughly 200nm after 5s. Factors determining nucleation, growth, and coalescence of metal clusters are identified and investigated.
Microstructure of Physical Vapour Deposited Ti-Si-N Coatings
Authors: Kauffmann Florian , Dehm Gerhard , Arzt Eduard , Schier Veit , Henke Sascha , Schattke Alaexander , Beck Thomas
Published: April 2011

The influence of Si on the microstrucure of Ti-Si-N coatings was studied, since it controls the mechanical properties of the coatings. At low Si-contents columnar {111}-textured TiN grains form. Increasin the Si-content to >4at% causes a transition to equiaxed {200}-textured TiN grains. The equiaxed TiN grains reveal grain diameters of ∼6 nm for coatings containing 11 at% Si.
Formation of Ferromagnetic FePt Nanoparticles by Ion Implantation
Authors: White C. W. , Withrow S. P. , Budai J. D. , Boatner L. A. , Sorge K. D. , Thompson J. R. , Beaty K. S. , Meldrum A.
Published: April 2011

Oriented ferromagnetic FePt nanoparticles with the face-centered tetragonal L10 structure were produced in Al2O3 single crystal hosts by ion implantation and annealing. Both the orientation and particle-size of the FePt particles depend strongly on the implantation conditions. The magnetic coercivities are extremely high, reaching values in excess of 20 kOe for Pt concentrations of ∼45% in the FePt alloy. Ferromagnetic FePt nanoparticles were also produced in amorphous SiO2 by ion implantation and annealing.