bluuebunny/crossref_metadata_2025_split huggingface dataset:
Casimir Forces Between Nanoparticles and Substrates
Authors: Román-Velázquez C. E. , Noguez Cecilia , Villarreal C. , Esquivel-Sirvent R. 
Published: April 2011

ABSTRACTWe study the Casimir force between a nanoparticle and a substrate using a spectral representation formalism. We consider the interaction of metal nanoparticles with different substrates within the dipolar approximation. The force is calculated as a function of the distance between the particles and the substrate. The particles are made of gold or potassium spheres, and the substrate is titanium dioxide, sapphire or a perfect conductor.
Tunneling Spectroscopy of short atomic chains.
Authors: Stein Jeremy , Zypman Fredy R. 
Published: April 2011

ABSTRACTIn this paper we present results on transmission-energy and current-voltage curves for a Scanning Tunneling Microscopy probe in the presence of an atomic chain, operating in spectroscopy mode. We compare the results with independently calculated density of sates. Finally, we propose algorithms to process this experimental information to obtain chemical specificity and position of impurities in the chain.
Influence of Substrate on In-Plane Electrical Conduction of CuPc Nano-Crystals
Authors: Nakamura Masakazu , Watanabe Masatoshi , Maruyama Tsuyoshi , Iizuka Masaaki , Kudo Kazuhiro 
Published: April 2011

ABSTRACTWe have investigated the conductivity variation of copper phthalocyanine nano-crystals deposited on SiO2 and mica. The density of surface hydroxyl group on SiO2 was estimated to be more than 10 times larger than that on mica by X-ray photoelectron spectroscopy. The grown crystals on both substrates were categorized to be a-axis orientation of α–form. Conductance-distance (G-d) measurements for various crystalline grains having different heights have been carried out with current imaging using atomic force microscope. The obtained conductivity vs. crystal height plot indicates that lower height crystals have higher conductivities on both surfaces. Besides, the lower height crystals on SiO2 have higher conductivity than those on mica. These results suggest that the electrons in the bottommost molecular layer are transferred to the electrophilic functional groups on the substrate surface. Such a phenomenon at organic semiconductor/insulator interface is reported for the first time.
Damping and Stiffness Enhancement in Composite Systems with Carbon Nanotubes Films
Authors: Lass E. A. , Koratkar N. A. , Ajayan P. M. , Wei B. Q. , Keblinski P. 
Published: April 2011

ABSTRACTStructural damping is an essential design parameter for many engineering applications. We demonstrate here the potential for the use of multi-walled carbon nanotube films in structural systems where vibrational energy dissipation is important. These films can provide a light weight, minimally intrusive alternative to conventional damping materials such as visco-elastic polymers. In addition, because of their multifaceted properties, damping materials utilizing carbon nanotubes are expected to be superior to traditional materials and may enhance the performance of the system by increasing structural stiffness and thermal stability.
Radiolytic Synthesis of Bimetallic Nanoparticles with High Aspect Ratio
Authors: Doudna C. M. , Bertino M. F. , Pillalamarri S. , Blum F. D. , Tokuhiro A. T. , Chattopadhyay S. , Terry J. 
Published: April 2011

ABSTRACTWe present a technique to synthesize high aspect ratio metallic nanostructures based on the radiolysis method. In our experiments, we use gamma rays to irradiate aqueous solutions containing Ag and Pt ions and a water-soluble polymer. The aspect ratio of the nanoparticles is controlled by varying the radiation dose rate, the type of polymer, and the type of counter ions. Transmission electron microscopy shows that wire-like structures composed of grains with a face centered cubic (fcc) structure can be formed with a length of up to 3.5μm and typical diameters between 5 and 12nm. X-Ray absorption spectroscopy shows that Ag and Pt do not form an alloy, but remain segregated.
Preferred Orientation in Fibers of Hipco Single Wall Carbon Nanotubes from Diffuse X-Ray Scattering
Authors: Zhou W. , Winey K. I. , Fischer J. E. , Ramesh S. , Saini R. K. , Ericson L. M. , Davis V. A. , Pasquali M. , Hauge R. H. , Smalley R. E. 
Published: April 2011

ABSTRACTNeat Fibers of HiPco single wall carbon nanotubes extruded from strong acid suspensions exhibit preferred orientation along fiber axes. We characterize the extrusion-induced alignment using x-ray fiber diagrams and polarized Raman scattering, using a model which allows for some fraction of the sample to remain completely unaligned. We show that both x-ray and Raman data are required for a complete texture analysis of SWNT fibers.
Polymer-Attached Functional Inorganic-Organic Hybrid Nano-composite Aerogels
Authors: Liu Xipeng , Wang Mingzhe , Risen William M. 
Published: April 2011

ABSTACTNovel materials in which modified inorganic-organic hybrid silica aerogels are attached to polymer chains have been synthesized. The aerogels are based on chitosan, a bioderived polymer from chitin, and they contain silica. The first stage of the modifications includes attachment of isocyanate, amine onto the chitosan chains embedded within the aerogel. These groups are employed in the second stage to develop the reactions required to “string” aerogel particles along functionalized linear polymers or to employ these polymers to crosslink the composite aerogels. The initial chitosan-silica aerogel particles have an ultimate size of about 2nm, and their functionally modified forms were reacted at sizes up to 1 m. These aerogels can take up and hold dyes and water-soluble drugs. The chemistry to synthesize polyamino-siloxane based aerogel composite was discussed. In addition, two approaches to synthesize PHEMA aerogel hybrid were studied.
Plasticity in Nanomaterials
Authors: Zhan Guo-Dong , Kuntz Joshua D. , Wan Julin , Mukherjee Amiya K. 
Published: April 2011

ABSTRACTThere have been many predictions of the reinforcing effects of carbon nanotubes in various composite matrices but large improvements in properties have not yet been convincingly demonstrated. In the present study, we have successfully realized this possibility in reinforcing nanocrystalline alumina. Fully dense single-wall carbon nanotubes (SWCN)/Al2O3 nanocomposites with nanocrystalline alumina matrix have been fabricated at sintering temperatures as low as 1150°C by spark-plasma-sintering (SPS). A fracture toughness of 9.7 MPam1/2, nearly three times that of pure nanocrystalline alumina, has been achieved in the 10 vol.% SWCN/Al2O3 nanocomposite. Moreover, high-strain-rate superplasticity has been achieved in Al2O3/ZrO2/MgAl2O4 nanocomposite with truly nanocrystalline grain size of 100 nm. Compression superplastic tests were conducted in the temperature range of 1300–1450°C at strain rates 10-3-10-1 s-1. The results generated a stress exponent of ∼ 2 and an activation energy of ∼ 620 kJ/mol.
Coating of Ultrathin Polymer Films on Carbon Nanotubes by a Plasma Treatment
Authors: He Peng , Lian Jie , Shi Donglu , Wang Lumin , Mast David , van Ooij Wim J. , Schulz Mark 
Published: April 2011

ABSTRACTUltrathin polymer films have been deposited on both single- and multi-wall carbon nanotubes using a plasma polymerization treatment. HRTEM experiments showed that an extremely thin film of the pyrrole layer (2–7 nm) was uniformly deposited on the surfaces of the nanotubes including inner wall surfaces of the multi-wall nanotubes. Time-of-Flight Secondary ion mass spectroscopy (TOFSIMS) experiments confirmed the nanosurface deposition of polymer thin films on the nanotubes. The deposition mechanisms and the effects of plasma treatment parameters are discussed.
Arc Plasma Synthesis of Nanostructured Fe Powder
Authors: Lee Gil-Geun , Kim Sung-Duck 
Published: April 2011

ABSTRACTTo investigate the effect of the parameters of the arc plasma process on the characteristics of the iron nano powder, the hydrogen volume fraction in the powder synthesis atmosphere was changed from 10% to 50%. The particle size, phase structure and magnetism of the synthesized iron powder were studied using the FE-TEM, XRD and a vibration magnetometer at room temperature. The particle size increased simultaneously with the increase in the hydrogen volume fraction, and the particle size ranged from about 20nm to 100nm with the change of the hydrogen volume fraction increasing from 10% to 50%. The synthesized iron powder particle had a shell-core structure composed of the crystalline a-Fe in the core and the crystalline Fe3O4 in the shell. The iron nano powder synthesized under the high hydrogen volume fraction condition had a higher saturation magnetism and lower coercive force than the values of the one synthesized under the low hydrogen volume fraction condition.
Characterization of Nanoparticle Films and Structures Produced by Hypersonic Plasma Particle Deposition
Authors: Perrey Christopher R. , Thompson Ryan , Barry Carter C. , Gidwani Ashok , Mukherjee Rajesh , Renault Thierry , McMurry P. H. , Heberlein J. V. R. , Girshick S. L. 
Published: April 2011

ABSTRACTThere is great potential for the use of nanostructures in numerous applications. Investigation of nanoparticle films and structures is an important area of research for the production of nanoengineered devices. However, for these devices to become a reality, a production method that can yield high-rate synthesis of nanostructured powders is necessary. The hypersonic plasma particle deposition (HPPD) process has been shown to be capable of such high-rate production of nanoparticle films and structures. Versatile in its ability to manufacture nanoparticles of different chemistries HPPD also has the capability of in situ particle consolidation and assembly. In this study, chemically diverse films and structures have been produced by HPPD on a variety of substrates. Using novel specimen preparation techniques, these nanoparticles have been characterized by TEM. Fundamental issues of importance have been investigated for both the nanoparticle structure and the constituent nanoparticles. These issues include nanoparticle crystallinity and defect structure. The chemical homogeneity and structural characteristics of the deposition are also investigated. This application of microscopy to aid process development has resulted in insights into the nanoparticle formation process and the dynamics of the HPPD process.
Mechanical and Thermoviscoelastic Behavior of Clay/Epoxy Nanocomposites
Authors: Abot Jandro L. , Yasmin Asma , Daniel Isaac M. 
Published: April 2011

ABSTRACTThe study of organic-inorganic nanocomposites has become relevant in recent years since these materials exhibit synergistic properties derived from the two components. Thermosetting polymers like epoxies that have high mechanical properties provide a baseline for further improvement with the addition of nanoclay particles. These nanocomposites can be used as the matrix of a fiber reinforced composite and lead to higher matrix dominated mechanical properties including elastic modulus, strength and fracture toughness. This study concentrates on the mechanical and thermoviscoelastic properties in the glassy regime of nanocomposites prepared by direct mixing. The elastic modulus of the nanocomposites was found to improve with respect to the pure epoxy modulus at the expense of both tensile strength and ductility regardless of clay content. The glass transition temperature was also found to decrease as well. The morphology of the nanocomposites was studied and correlated with the aforementioned properties.
Preparation and Characterization of Alumina based TiNn and SiCn Composites
Authors: Carlsson Mats , Johnsson Mats , Pohl Annika 
Published: April 2011

ABSTRACTCeramic composites containing 2 and 5vol. % of nanosized commercially available TiN and SiC particles in alumina were prepared via a water based slurry processing route followed by spark plasma sintering (SPS) at 75 MPa in the temperature range 1200–1600°C. Some of the samples could be fully densified by use of SPS already after five minutes at 1200°C and 75 MPa. The aim was to control the alumina grain growth and thus obtain different nano-structure types. The microstructures have been correlated to some mechanical properties; e.g. hardness and fracture toughness.
Structure and elastic properties of immiscible LDPE-PP blends: dependence on composition
Authors: Petronyuk Julia S. , Priadilova Olga V. , Levin Vadim M. , Ledneva Olga A. , Popov Anatolii A. 
Published: April 2011

ABSTRACTLocal elastic properties and microstructural features of low-density polyethylene-polypropylene (LDPE-PP) blends have been studied by microacoustical technique, differential scanning calorimetry and infrared spectroscopy. Focused ultrasonic beam of acoustic microscope has been employed to measure elastic wave velocities, bulk and shear elastic moduli and Poisson ratio. The experiments show that the mechanical properties of immiscible LDPE-PP blends are non-additivily changeable in relation to ones of primary gomopolymers. Maximum of the moduli values is achieved with small addition of LDPE to PP. Additional drawing of bipolymer shows essential increasing of orientation ability for PP chains in 5/95 – 10/90 % LDPE-PP compositions. DSC curves show no significant deviations in melting temperature and crystallinity degree for different compositions of PP and LDPE phases. Internal microstructure has been imaged for the blends by acoustic microscopy technique. It allows revealing dispersivity of components over the blend body.
The Development of Alternative Molds for Micromolding
Authors: Garino Terry , Cesarano Joseph , Morales Alfredo 
Published: April 2011

ABSTRACTMicromolding is a recently developed technique for fabricating parts in the millimeter size range with minimum features and dimensional tolerances less than 10 μm. This degree of precision is achieved by fabricating a master using the LiGA process. The molds made from the master are then filled with powder of the desired material to form parts that are then released from the mold and sintered to high density. Currently, molds are made of either poly(methyl)methacrylate (PMMA) or poly(dimethylsiloxane) (silicone rubber, PDMS). The PMMA molds must be dissolved to release the parts using a solvent that limits the choice of binder used to hold together the powder in the part. The PDMS molds are soft and therefore not suitable for lapping the parts prior to removal from the mold. Recently, two new types of molds materials have been investigated that can be removed utilizing a phase change, either melting or sublimation. The development of these new mold materials, which allow a wider choice of binders, will be described.
A Chemical Sensor Using Neurons and a 3-D Micro-fluidic Chip
Authors: McNally H. , Kufluoglu H. , Akin D. , Grimmer J. , Walker J. , Shi R. , Borgens R. , Bashir R. 
Published: April 2011

ABSTRACTIn recent years, there has been a merger of microelectronics and biological sciences to develop integrated nano and micro-scale biosensors or biochips. The implementation of portable, rapid and economic methods for detecting different biological species on a chip will benefit from the development of electronic means for the analysis of cells. Neurons are very attractive as chemical sensors due to their sensitivity to specific toxins and their unique electrical properties. The use of closed well micro-fluidic devices for the growth of neurons has not been explored extensively. In this work, we will describe surface preparation techniques to enhance the neuronal cell viability and growth on microfabricated surfaces. We have fabricated micro-fluidic bio-chips for the trapping of neurons and to examine their growth. Neural cells are maintained in a chamber on the chip with fresh nutrient media continuously flowing through the chamber. The temporal viability of the neural cells within the chip will be reported. The long-term goals of the project include electrically measuring the viability of the cells inside the micro-fluidic chambers.
Strain Gradient Effect in Cone Indentation
Authors: DiCarlo Anthony A. , Yang Henry T. Y. , Chandrasekar Srinivasan 
Published: April 2011

ABSTRACTA size effect is known to exist in the strength and hardness of metals at small length scales. For example, the hardness of a pyramid indentation at the macro-scale is constant and typically independent of indentation size due to the self-similar feature of the indentation. But, at the meso-scale, this hardness has been observed to increase with decreasing indentation size. This increase has been attributed to the influence of strain gradient on the flow stress. At this point, the contribution of a rotational gradient to the hardness is unclear.This study investigates the sensitivity of the hardness to rotational strain gradients through a Cosserat continuum. Finite element simulation of cone indentation is employed to conduct this investigation. The effect of varying indentation strain fields is modeled using indentation with cones of varying angles. The results demonstrate the role of rotational gradients in indentation.
<0001> channeling stopping power of MeV He+ ions in 4H- and 6H-SiC.
Authors: Nipoti Roberta , Letertre Fabrice 
Published: April 2011

ABSTRACT4H-SiC and 6H-SiC thin films as top surface layers of SiCOI wafers and Rutherford Back Scattering experiments with He+ ions in the energy range 0.9 – 2.2 MeV were used for measuring the He+ ions <0001> channeling stopping power with respect to the SiC random one. The film thicknesses were in the range 270–360 nm. The ratio between axial and random stopping power values decreased for increasing energy values and was higher for the 6H polytype with respect to the 4H one, i.e. it ranged from 0.85 to 0.72 for the former and from 0.80 to 0.66 for the latter.
Radial distribution functions of amorphous silicon carbide
Authors: Ishimaru Manabu , Bae In-Tae , Hirotsu Yoshihiko 
Published: April 2011

ABSTRACTAtomistic structures of amorphous silicon carbide generated by energetic particles were examined by electron diffraction techniques in combination with imaging plates. Atomic pair distribution functions revealed that not only heteronuclear (silicon-carbon) bonds but also homonuclear (silicon-silicon and carbon-carbon) bonds exist in the first coordination shell of amorphous silicon carbide induced by ion- or electron-beam-irradiation. Structural changes from amorphous silicon carbide to amorphous silicon were observed under the electron irradiation.
Four Current Examples of Characterization of Silicon Carbide
Authors: Bai S. , Ke Yue , Shishkin Y. , Shigiltchoff O. , Devaty R. P. , Choyke W. J. , Strauch D. , Stojetz B. , Dorner B. , Hobgood D. , Serrano J. , Cardona M. , Nagasawa H. , Kimoto T. , Porter L. M. 
Published: April 2011

ABSTRACTA description is given of the profiling of CVD grown 3C SiC on undulant (001) Si using low temperature photoluminescence (LTPL). Inelastic neutron scattering (INS) and X-ray Raman scattering (XRS) are compared for acoustical modes of 4H SiC. Schottky barrier heights are obtained for 4H and 6H SiC on different crystal faces using three different measuring techniques. Scanning electron microscopy (SEM) is used to display a variety of porous SiC morphologies achieved in n-type and p-type SiC.This paper is intended to be the introduction to the “CHARACTERIZATION” section of this volume. To serve this purpose we illustrate the subject matter with new results using four distinct experimental techniques.
Hall Scattering Factor of Holes and Shallow Defect Centers in Aluminum-doped SiC
Authors: Pensl Gerhard , Ciobanu Florin , Krieger Michael , Laube Michael , Reshanov Sergey , Schmid Frank , Wagner Günter , Nagasawa Hiroyuki , Schöner Adolf 
Published: April 2011

ABSTRACTThe Hall scattering factor of holes rH,h(T) in 4H- and 6H-SiC is determined by comparing the temperature-dependent free hole concentration p(1/T) obtained from Hall effect and from the neutrality equation with defect parameters, which are independently determined by SIMS and C-V measurements. rH,h(T) strongly deviates from 1 and assumes values between 1.4 and 0.5 at temperatures ranging from 100K to 800K. rH,h(T) is identical for 4H-and 6H-SiC within the measurement uncertainty. Al-doped SiC epilayers of the 3C-, 4H- and 6H-polytype were investigated with admittance spectroscopy and DLTS prior to and subsequent to processing steps. Depending on the SiC polytype, a different number of shallow acceptors is observed, which are thermally stable up to high temperatures (1700°C).
Experimental Studies and Thermodynamic Modeling of the Interaction of O2 with SiC
Authors: Song Y. , Smith F. W. 
Published: April 2011

ABSTRACTWe report on experimental studies and thermodynamic modeling of the reaction of O2 with the 4H- and 6H-SiC surfaces at high temperatures. This reaction leads to the growth of passivating SiO2 layers at high O2 pressures, etching of the surfaces at lower pressures, and enhancements of the surface segregation of carbon at still lower pressures. A pressure-temperature phase diagram for the oxidation of SiC is presented. Evidence for the thermal decomposition of the SiO2 layer on SiC is also presented.
SiC BJT's for High Power Switching and RF Applications
Authors: Agarwal Anant , Ryu Sei-Hyung , Capell Craig , Richmond James , Palmour John W. , Phan Binh , Stambaugh Jerry , Bartlow Howard , Brewer Ken 
Published: April 2011

ABSTRACTIn this paper, high performance, high voltage NPN bipolar junction transistors in 4H-SiC are presented for applications in low frequency (< 5 MHz) power conversion systems as well as in RF (425 MHz) power amplifiers. The power BJTs for low frequency switching applications were designed to block 1300 V and showed a specific on-resistance of 8.0 mohm-cm2, which outperforms all SiC power switching devices ever reported. Moreover, these transistors show a positive temperature coefficient in the on-resistance and a negative temperature coefficient in the current gain, which enable easy paralleling of the devices. In addition, RF BJTs were designed, fabricated and tested for operation at UHF frequencies. The common emitter breakdown voltage was in excess of 500 V consistent with the 5 micron collector thickness. For VCC = 20 V, fT peaked at about 1.5 GHz. A single cell was measured in common emitter mode with a collector supply voltage of 80 V in class AB at 425 MHz. A 100 μs pulse width with 10% duty cycle was used. A maximum output power of 50 W for a single cell was achieved. The peak large signal power gain was 9.6 dB. The collector efficiency at the power output of 50 W was 51% with a power gain of 9.3 dB. This represents the first demonstration of a SiC RF BJT.