bluuebunny/crossref_metadata_2025 huggingface dataset:
Glass Formation Dependence on Casting Atmosphere in a Zr-Al-Ni-Cu-Pd Alloy System
Authors: Setyawan Albertus Deny , Kato Hidemi , Saida Junji , Inoue Akihisa
Published: April 2011

A Zr65Al7.5Ni10Cu17.5-xPdx (x=0-17.5 at. %) alloy system is found to exhibit a unique dependence of glass-forming ability (GFA) on casting atmosphere during mold-casting process. High-Pd containing alloys (x=7.5-17.5) showed a remarkable increase of critical size (dc) for glass formation, in contrast with the low-Pd containing alloys (x=0-5) in which no significant change in dc was observed, as the pressure of Ar atmosphere varied from vacuum to ambient. The origin of the phenomenon has been successively unveiled by correlating the cooling characteristic during casting process and phase transformation behavior during continuous cooling of the alloy system. The consequence in the structure and property control is investigated and discussed in detail.
Nanoindentation Analysis of Plasticity Evolution during Spherical Microindentation of Bulk Metallic Glass
Authors: Yoo Byung-Gil , Jang Jae-il
Published: April 2011

Unlike most of crystalline metals, metallic glasses are known to exhibit a fully-plastic behavior or work softening during mechanical deformation. To analyze the characteristics of the deformed region, here a series of instrumented micro- and nano-indentation experiments were performed on a Zr-based bulk metallic glass (BMG) with geometrically self-similar sharp indenter as well as spherical indenters. First, we performed instrumented micro-indentation tests with a spherical indenter on the bonded interfaces of the BMGs. Although adhesive (used for bonding the interfaces) might significantly affect the deformation mode by reducing the constraint, the evolution of subsurface plasticity during spherical indentation was clearly observed. Subsequently, the subsurface plasticity underneath the hardness impressions was systematically examined through nanoindentation. The results are discussed in terms of major change in mechanical responses of BMGs before and after indentation-induced deformation.
Mechanical Properties of Sputtered Silicon Oxynitride Films by Nanoindentation
Authors: Liu Yan , Lin I-Kuan , Zhang Xin
Published: April 2011

Silicon oxynitride (SiON) films with different oxygen and nitrogen content were deposited by RF magnetron sputtering. Fourier-transform infrared (FT-IR) spectroscopy study revealed that co-sputterred SiON films were composed of one homogeneous phase of random bonding O-Si-N network. Time-dependent plastic deformation (creep) of SiON films were investigated by depth-sensing nanoindentation at room temperature. Results from nanoindentation creep indicated that plastic flow was relatively less homogenous with increasing nitrogen content in film composition. A deformation mechanism based on atomic bonding structure and shear transformation zone (STZ) plasticity theory was proposed to interpret creep behaviors of sputtered SiON films.
Indentation of Nonlinearly Viscoelastic Solids
Authors: Oyen Michelle L
Published: April 2011

Much recent attention has been focused on the indentation of linearly viscoelastic solids, and analysis techniques have been developed for polymeric material characterization. However, there has been relatively little progress made in the development of analytical approaches for indentation of nonlinearly viscoelastic materials. Soft biological tissues tend to exhibit responses which are nonlinearly viscoelastic and are frequently modeled using a decomposition of the relaxation or creep function into a product of two functions, one time-dependent and the other stress- or strain-level dependent. Consideration here is for soft biological tissue-like responses, exhibiting approximately quadratic stress-strain behavior, which can be alternatively cast as linear dependence of elastic modulus on strain level. An analytical approach is considered in the context of indentation problems with flat punch, spherical and conical indenter shapes. Hereditary integral expressions are developed and solved for typical indentation experimental conditions including indentation creep, load-relaxation and monotonic constant load- or displacement-rate tests. Primary emphasis is on the deconvolution of material and geometrical nonlinearities during an indentation experiment. The simple analytical expressions that result from this analysis can be implemented for indentation characterization of soft biological tissues without the need for computationally- intensive inverse finite element approaches.
Instrumented Indentation Contact with Sharp Probes of Varying Acuity
Authors: Morris Dylan J.
Published: April 2011

While elastic and plastic material property extraction from instrumented indentation tests has been well-studied, similarly-based fracture property measurement remains difficult. Furthermore, estimation of the fracture toughness requires measurement of the crack lengths from a micrograph, which makes nano-scale indentation toughness measurement expensive and difficult. Initiation and propagation of cracks on the nano-scale requires a more acute indenter than a Berkovich or sphere, such as the cube-corner pyramid. Experiments described here were performed on a range of elastic, plastic and brittle materials with diamond indenters of acuity varying between the Berkovich and the cube-corner. These experiments reveal some of what is changed and what remains the same, when the acuity of the probe is changed, when fracture is initiated at the contact, or both. A preliminary model for the physical origin of the extra crack-driving power of acute probes is presented in light of these, and complementary macro-scale in-situ indentation experiments. This work provides the basis for development of instrumented indentation-based nano-scale toughness measurement.
Viscoelastic Behavior of a Centrally Loaded Circular Film Being Clamped at the Circumference
Authors: Oyen Michelle L , Liu Kuo-kang , Wan Kai-tak
Published: April 2011

A new theoretical model is constructed for the viscoelastic response of a clamped circular membrane deformed by a spherical indenter, using the classical Maxwell and Standard Linear Solid (SLS) constitutive equations. Preliminary stress-relaxation experiments are performed for a hydrogel membrane and the corresponding data fitted to the SLS-based viscoelastic model.
Emerging Nanomaterials for Nuclear Radiation Detectors
Authors: Osinski Marek
Published: April 2011

Nanosize devices have attracted tremendous interest over the last few years for a wide range of biomedical, biochemical sensing, and optoelectronic applications. So far, however, their potential has largely eluded the nuclear detection community. In this paper, the current status of the emerging nanomaterials for nuclear detection applications is reviewed. Recent preliminary data are presented, and the potential improvements in the detector cost, reliability, and performance the nanosize devices have to offer are discussed.
MEMS Lubrication: An Atomistic Perspective of a Bound + Mobile Lubricant
Authors: Irving Douglas Lee , Brenner Donald W
Published: April 2011

The adhesive pressure needed to separate two ocatdecyltrichlorosilane (ODTS) coated surfaces both with and without the addition of tricresyl phosphate (TCP) as a function of separation rate is characterized using molecular dynamics simulation. The simulations predict that when TCP is added between surfaces the adhesive pressure needed for separation is reduced compared to the system containing ODTS only. Both the adhesive pressure and the break up of the TCP layers exhibit a separation rate dependence that appears unrelated to the rate of diffusion of TCP on the ODTS. The ability of the TCP to remain localized to defected areas of the ODTS layer upon normal separation of the contact is also characterized. It is found that the TCP remains localized to defect sites, which effectively coats the damaged area.
Indentation Characterization of Fracture Toughness and Interfacial Strength of PECVD Nitrides after Rapid Thermal Annealing
Authors: Yan H-Y , Ou K-S , Chen K-S
Published: April 2011

This work presents the result of mechanical characterization of the fracture toughness and interfacial strength of PECVD silicon nitride films deposited on silicon subjected to rapid thermal annealing (RTA) processing between 200 and 800 °C. Both micro- and nano-indentation techniques are employed to perform the experiments. In conjunction with the model proposed by Marshall and Lawn for data reduction, the fracture toughness of un-heat treated nitride is obtained as 2.2 MPa√m based on a series of Vickers micro-indentation tests and this value is essentially unchanged if the RTA temperatures are below 400°C. Further increase in RTA temperature would significantly enhance the fracture toughness. On the other hand, using nanoindentation testing in conjunction with the model proposed by Marshall and Evans, the interfacial strength between the nitride and silicon is determined as 17.2 J/m2 for un-heat treatment nitrides and it could also be significantly enhanced by RTA processes with temperatures exceeding 400°C. These results should be useful for related MEMS or IC structure fabrication for the concerns of maintaining the structural integrity and improve fabrication performance in related applications.
A Novel Micro Tensile Testing Instrument with Replaceable Testing Specimen by Parylene Passivation Technique
Authors: Lau Yung-Dong , Chang Tso-Chi , Hocheng Hong , Chen Rongshun , Fang Weileun
Published: April 2011

This study has successfully demonstrated a novel tensile testing approach to mount the thin film test specimen onto the MEMS instrument using microfabrication process. The MEMS instrument consists of thermal actuator, differential capacitance sensor, supporting spring. The thermal actuator applies tensile load on the test specimen to characterize the Young's modulus and the residual stress of thin films. As compare with the existing approaches, the problems and difficulties resulting from the alignment and assembly of thin film test specimens with the testing instrument can be prevented. Furthermore, the parylene passivation technique of MEMS fabrication process allows the changing of testing film materials easily. In application, the present approach has been employed to determine the Young's modulus and the residual stress of Al films.
Elastic and Viscoelastic Characterization of Polydimethylsiloxane (PDMS) for Cell-Mechanics Applications
Authors: Lin I-Kuan , Liao Yen-Ming , Liu Yan , Chen Kuo-Shen , Zhang Xin
Published: April 2011

The mechanical properties of polydimethylsiloxane (PDMS) were characterized by using uniaxial compression, dynamic mechanical analysis (DMA), and nanoindentation tests as well as finite element simulation methods. A five-parameter linear solid model was used to emulate the behavior of PDMS. The study results indicated that the effect of viscoelasticity affected the PDMS pillar arrays significantly. The traditional approach for calculating the cell force basing on the linear elastic mechanics could result in considerable errors.
Modification of Conductivity and of Mechanical Properties of Electroactive Polymer (EAP) Thin Films by Titanium Ion Implantation
Authors: Niklaus Muhamed , Rosset Samuel , Dadras Massoud , Dubois Philippe , Shea Herbert R.
Published: April 2011

We present a study of the influence on Young's modulus, stress and electrical conductivity of poly-dimethylsiloxane membranes implanted with titanium ions at energies from 5 to 35 keV, with doses up to 8×1016 ions/cm2. The motivation for this study was to find the optimum implantation conditions to create electrodes for microfabricated dielectric electroactive polymer actuators, which must combine low resistivity with low stiffness. Two implantation techniques are used, Filtered Cathodic Vacuum Arc (FCVA) and the more conventional Low Energy broad beam Implanter (LEI). Of the two, it is found that the FCVA implanter is much better suited to create compliant electrodes.
Optically Actuated Deformable Micro-Mirrors for Adaptive Optics
Authors: Ribaudo Troy , Li Jin , Haji-saeed Bahareh , Khoury Jed , Goodhue William
Published: April 2011

In this paper we report on our latest efforts to fabricate and characterize optically actuated deformable micro mirrors for wavefront correction in an adaptive optics system. The optically actuated DMM device consists of a Silicon Nitride (Si3N4) thin film patterned into a spring plate array, an SU-8 photoresist supporting structure that provides the space through which the mirror is allowed to deform, and a PIN photodiode which allows an optical control signal to actuate the DMM.
Compliant MEMS Motion Characterization by Nanoindentation
Authors: Choueifati Joseph , Lusk Craig , Pang Xialou , Volinsky Alex A.
Published: April 2011

Large out-of-plane displacements can be achieved when compliant mechanisms are utilized in MEMS. While mathematical and macroscopic modeling is helpful in building original designs, the actual MEMS device motion needs to be characterized in terms of the forces and displacements. A nanoindentation apparatus equipped with Berkovich diamond tip was used in an attempt to actuate and characterize the motion of the Bistable Spherical Compliant Micromechanism with a nonlinear (approximately cubic) mechanical response. Based on the obtained lateral force-displacement data it was concluded that the Berkovich diamond tip was too sharp, thus cutting through the polysilicon material of the MEMS device.
Protection Layer Influence on Capacitive Micromachined Ultrasonic Transducers Performance
Authors: Jeanne Edgard , Meynier Cyril , Teston Franck , Certon Dominique , Felix Nicolas , Roy Mathieu , Alquier Daniel
Published: April 2011

For MEMS technology, reliability is of major concern. The implementation of a protection and passivation layer, that may easily enhance reliability of capacitive Micromachined Ultrasonic Transducers (cMUTs) must be done without degrading device performance. In this work, realization, simulation and characterization of passivated cMUT are presented. Two materials, SiNx and Parylene C, were selected with regard to their mechanical and physical properties as well as their compatibility with device processing. Particular attention was paid on layer deposition temperature to avoid a structural modification of the top aluminium electrode and, hence, a membrane bulge. The characterization results are in good agreement with the simulations. The SiN passivation layer clearly impact device performance while Parylene C effectiveness is clearly pointed out even through ageing characterizations. If SiNx layer can be used for passivation with particular precautions, Parylene is definitely an interesting material for cMUT passivation and protection.
Relationship between film stress and dislocation microstructure evolution in thin films
Authors: Fertig Ray Stuart , Baker Shefford P.
Published: April 2011

Metals with one or more dimensions in the submicron regime are widely used in MEMS devices. Device stresses often exceed the strength of the corresponding bulk material by an order of magnitude and can lead to a variety of mechanical failures. At moderate temperatures, high stresses occur because dislocations are unable to move to relax the stress. This is partly because of an elastic dimensional constraint, but complex dislocation behavior, such as junction formation, annihilation, and nucleation, are also observed. In this report, we present results from analytical models, cellular automata simulations, and large-scale dislocation dynamics simulations of submicron films to examine the relationship between dislocation interactions and material strength. Our results reveal a complex relationship between dislocation interactions and stress inhomogeneity that arises from the stress fields of the dislocations. We show that the stress inhomogeneity increases both the likelihood of interactions and acts to increase the strain hardening rate.
Optical Waveguides Embedded in PCBs - A Real World Application of 3D Structures Written by TPA
Authors: Houbertz Ruth , Wolter Herbert , Schmidt Volker , Kuna Ladislav , Satzinger Valentin , Wüchter Christoph , Langer Gregor
Published: April 2011

The integration of optical interconnects in printed circuit boards (PCB) is a rapidly growing field worldwide due to a continuously increasing need for high-speed data transfer. There are any concepts discussed, among which are the integration of optical fibers or the generation of waveguides by UV lithography, embossing, or direct laser writing. The devices presented so far require many different materials and process steps, but particularly also highly-sophisticated assembly steps in order to couple the optoelectronic elements to the generated waveguides. In order to overcome these restrictions, an innovative approach is presented which allows the embedding of optoelectronic components and the generation of optical waveguides in only one optical material. This material is an inorganic-organic hybrid polymer, in which the waveguides are processed by two-photon absorption (TPA) processes, initiated by ultra-short laser pulses. In particular, due to this integration and the possibility ofin situpositioning the optical waveguides with respect to the optoelectronic components by the TPA process, no complex packaging or assembly is necessary. Thus, the number of necessary processing steps is significantly reduced, which also contributes to the saving of resources such as energy or solvents. The material properties and the underlying processes will be discussed with respect to optical data transfer in PCBs.
Micro/Nano Fabrication of Surface Architectures on Polymers and Copolymers Using Direct Laser Interference Patterning
Authors: Acevedo Diego , Lasagni Andrés , Barbero Cesar , Muecklich Frank
Published: April 2011

Novel surface engineering techniques of polymeric materials are essential to produce advanced topographies which could for example serve to modulate cell and tissue response in bio-materials. Direct Laser Interference Patterning (DLIP) permits the fabrication of repetitive arrays and microstructures by irradiation of the sample surface with coherent beams of light. Furthermore, the most important advantage of this method is that no additional process steps are required in comparison with other top-down or bottom-up techniques. In this study, we report a novel method for the advanced design of architectures in polymers using a single step process, as well as photo-activation of polymers with low absorption coefficient using a second polymer with relative high absorption coefficient. Previously calculated interference patterns using the well known interference theory could be directly produced on polymeric surface. Moreover, the cross-section of the structured polymers changes depending on the intensity of the laser beams, and photomachinability of polymers is highly influenced by laser wavelength. High absorbance of the polymeric materials at specific wavelengths allows the reduction of the laser intensity required to achieve a determined structure depth. For (60:40 %) polymethylmetacrylate/polystyrene copolymer substrate, different structures types were observed depending on the laser intensity including swelling and ablation of the material.
Atomic Layer Deposition on Quantities of Multiwalled Carbon Nanotubes
Authors: Cavanagh Andrew S. , Wilson Christopher A. , Weimer Alan W. , George Steven M.
Published: April 2011

Atomic layer deposition (ALD) was performed on quantities of multiwalled carbon nanotubes (MWCNTs) in a rotary reactor. Because of nucleation difficulties, Al2O3 ALD grew as nanospheres on the MWCNTs. After a NO2 nucleation treatment, Al2O3 ALD films grew conformally and noncovalently functionalized the surface of the MWCNT. This Al2O3 ALD film served as a platform for the growth of W ALD metal. The uncoated and ALD-coated MWCNTs were characterized with transmission electron microscopy and x-ray photoelectron spectroscopy. This study demonstrates that ALD can be performed on quantities of very high surface area MWCNT substrates.
EBI Joining Between Different Polymers Without Adhesive Materials
Authors: Sato Hironori , Iwata Keisuke , Tonegawa Akira , Nishi Yoshitake
Published: April 2011

Joining between Nylon-film and Silicone-rubber was successfully developed. Effects of EB-irradiation on joining strength of different polymers without adhesive materials were investigated by using homogeneous EB irradiation. The EB irradiation increased the joining strength of the joining sample between Nylon-film and Silicone-rubber. Excess EB-irradiation more than 0.3 MGy apparently decreased the joining strength. To discuss the influences of electron beam irradiation on the joining strength, ESR signals related to dangling bonds were observed. Since the EB irradiation produced detectable dangling bonds on Nylon-film, using dangling bonds probably joined the different polymers.
Effect of Crystallographic Structure of Substrate on Texture in Electrodeposited Ni Layers
Authors: Shimada Takafumi , Shibata Akinobu , Ishiyama Chiemi , Sone Masato , Higo Yakichi
Published: April 2011

Effect of substrate on the texture of electrodeposited Ni layer was investigated by using various substrates; Ni-P alloy (amorphous), pure Cu (fcc) and pure Ni (fcc). In the case of Ni-P and Cu substrates, deposited Ni layer shows the (115) fiber texture and its formation was not biased by substrate. On the other hand, the formation of texture is not independent of Ni substrate because its texture is not ideal fiber.

Near the interface between deposited Ni layer and Ni-P or Cu substrates, fine columnar grains were observed. In contrast, on Ni substrate there are coarse columnar grains ahead of continuous epitaxial region. It is considered that texture of deposited Ni layer is not independent of Ni substrate due to the fact that these columnar grains satisfy a certain orientation relationship with respect to substrate.
Specific Surface Free Energy of Ruby Thin Film Grown on Sapphire Single Crystals Studied by Contact Angle of Liquid Droplet
Authors: Suzuki Takaomi , Sugane Shintaro , Hidaka Miki , Teshima Katsuya , Oishi Shuji
Published: April 2011

Ruby thin film was grown on sapphire substrate by evaporation method of MoO3 flux. Small amount of Na2CO3 was added in order to decrease the evaporation rate of flux. The contact angles of liquids and crystal surfaces were measured for water and formamide droplets, and the specific surface free energy of each face of the crystal was calculated using Fowkes approximation and Wu's mean equations. The growth hillocks on the synthesized thin film were observed. The addition of Na2CO3 incrased the density of hillocks and the specific surface free energy was larger for the ruby thin film, which has larger number of hillocks.
New method of photochemical adhesion of fused silica glasses by using Xe2 excimer lamp
Authors: Funatsu Takayuki , Sato Yuji , Okamoto Yoshiaki , Murahara Masataka
Published: April 2011

A strong adhesion of two silica glasses or a silica glass and a different glass that creates properties of heatproof, no adhesive strain, and high transmittance in the region of ultraviolet [UV] was demonstrated with photochemical reaction by vacuum-ultraviolet [V-UV] light. It was confirmed that the adhesive strength of the silicone oil between the two silica glasses enhanced to 18 [MPa] after irradiation from 0 [MPa] before irradiation, that of the SiO2 and BK7 to 12.3 [MPa], and that of the SiO2 and TEMPAX®, to 10 [MPa], and that of the SiO2 and CLEARCERAM® to 7.4 [MPa]. Furthermore, the adhesive strain of the bonded sample was measured by 3-dimension roughness meter (ZYGO), and the results showed no adhesive strain. This sample had the bonding strength at 500 degrees Celsius.
Controlled Modification of Erbium Lifetime in Silicon Dioxide Film with Chromium or Titanium Coatings
Authors: Yu Nanfang , Bao Jiming , Belyanin Alexey , Mates Thomas , Troccoli Mariano , Capasso Federico
Published: April 2011

We report systematic measurements of the lifetime of the 1.54 μm transition of erbium implanted at different energies in SiO2films coated with titanium or chromium. The lifetime shows a strong reduction up to a factor of 20 with decreasing distance between the erbium and the metal coating. Our experiments combined with rigorous theoretical modeling demonstrate that a high degree of control over the radiative properties of erbium can be achieved in erbium-implanted materials.
A Simple Method to Self-Assemble Two-dimensional and Three-dimensional Superlattices of Gold Nanoparticles
Authors: Fu Tao , Qin Hai-Yan , Li Wen-Jiang , He Sailing
Published: April 2011

Citrate-capped gold nanoparticles with narrow diameter distribution were prepared by the reduction of chloroauric acid with borohydride. After the gold nanoparticles were transferred to toluene solution through ligand conformation change, close-packed two-dimensional nanocrystal lattices were obtained on transmission electron microscopy (TEM) copper grids by evaporating approximately 10 μL of concentrated particle dispersion. The formation of the thiolate gold nanoparticles was investigated by UV-visible absorption spectroscopy and FTIR spectra. The 2D Fourier transform power spectra of the monolayer confirmed the supperlattices' hexagonal symmetry. Furthermore, long-range-ordered bilayer superlattices, of which the nanoparticles in the top layer piled on the ones in the bottom layer, could also be observed by transmission electron microscopy.
Synthesis of III-V Nanocrystals by Co-reduction Reactions
Authors: Liu Zhaoping , Fang Jiye
Published: April 2011

This paper describes a co-reduction colloidal method for the synthesis of In-containing III-V nanocrystals (NCs) by using pnictogen halides (such as PCl3, AsCl3, and SbCl3) as the pnictogen-sources and superhydride (LiBH(C2H5)3) as the reducing agent. The syntheses were generally carried out in octadecene in the presence of fatty acids at ∼250 °C. The as-synthesized InP NCs were monodisperse in particle size and size distribution, whereas the InAs and InSb NCs showed relatively lower quality. The growth process of NCs was studied using InP as a model system.
Effects of Pigment Type and Dispersion on Photodegradation of Epoxy and Acrylic Urethane Films
Authors: Watson Stephanie , Forster Amanda , Tseng I-Hsiang , Sung Li-Piin , Lucas Justin , Forster Aaron
Published: April 2011

The effects of surface treatment, particle size, and concentration of titanium dioxide (TiO2) and its dispersion on the photodegradation of two resin systems, epoxy and acrylic urethane, were examined. A suite of techniques, including laser scanning confocal microscopy (LSCM) and attenuated total reflectance -Fourier transform infrared spectroscopy (ATR-FTIR), was used to follow the degradation process of TiO2/polymer films as a function UV exposure. LSCM was used to show that both pigment dispersion and durability of the polymer matrix influenced the generation of pits/holes in pigmented polymer film. The type of pigment had a greater influence on the more durable polymer matrix, the acrylic urethane system. The epoxy system showed the greatest extent of degradation regardless of the TiO2 choice. The LCSM results were supported by the ATR-FTIR data.
Osteoblast Behaviors on Novel Self-assembled Helical Rosette Nanotubes and Hydrogel Composites for Bone Tissue Engineering
Authors: Zhang Lijie , Ramsaywack Sharwatie , Fenniri Hicham , Webster Thomas J
Published: April 2011

To date, although traditional autografts and allografts have been standard methods to treat bone fractures and defects, the formation of biocompatible and injectable scaffolds to induce new bone growth is still a promising method to repair bone defects considering their minimally invasive and osteoinductive features. In this study, a novel bone tissue engineering scaffold based on the self-assembled properties of helical rosette nanotubes (HRNs) and biocompatible hydrogels (specifically, poly(2-hydroxyethyl methacrylate)-pHEMA) was designed to fill bone fractures and repair bone defects. HRNs are a new class of organic nanotubes with a hollow core 11 Å in diameter, which originate from the self-assembly of DNA base pair building blocks (guanine-cytosine) in aqueous solutions. Since HRNs can significantly change their aggregation state and become more viscous based on heating or when added to serum free medium at body temperature, HRNs may provide an exciting therapy to heal bone fractures as injectable bone substitutes. In addition, biocompatible hydrogels were used in conjunction with HRNs in this study to strengthen the bone substitutes and also to serve as a potential drug releasing carrier to stimulate new bone growth at such fracture sites. Two types of HRNs, one with a lysine side chain and the other conjugated to 1% and 10% RGD (arginine-glycine-aspartic acid) peptides on HRNs, were prepared and dispersed into hydrogels. Due to their nanometric features and the helical architecture of HRNs which biomimic collagen, results showed that these HRN hydrogel composites can significantly improve osteoblast adhesion compared to hydrogel controls. Furthermore, 0.01 mg/ml HRNs with RGD embedded in and coated on hydrogels can also enhance osteoblast attachment compared to 0.01 mg/ml HRNs with lysine side chains embedded in and coated on hydrogels. Results showed an increasing trend of osteoblast adhesion on these scaffolds with more RGD groups (10%) on HRNs. In this manner, nanostructured HRN hydrogel composites provide a promising alternative to repair bone defects considering the flexibility in the design of HRNs and their exceptional cytocompatibilty properties.
Mechanical Properties of Thermoplastic Polyolefin (TPO) /Clay Nanocomposites
Authors: Ruan Yong-Hong , Tjong Sie-Chin
Published: April 2011

Thermoplastic polyolefin (TPO) contained 30 wt.% PP and 70 wt.% SEBS-g-MA, and its nanocomposites reinforced with 0.3 -1.5 wt.% organoclay (OMMT; Cloisite 30B) by a two-step melt mixing followed by injection molding. The microstructure and mechanical behavior of the TPO/OMMT nanocomposites were investigated. X-ray diffraction measurements revealed the absence of basal diffracting peak of OMMT in TPO/OMMT, suggesting formation of intercalated/exfoliated nanocomposites. Tensile tests showed that the stiffness, yield strength and tensile strength of TPO can be enhanced by adding low loading levels of OMMT. Thus, OMMT can reinforce TPO due to their large aspect ratios. Moreover, there was no reduction in the impact strength of the TPO/OMMT nanocomposites associated with the clay additions.
Temperature Dependent Sensitivity Inversion in SnO1.8:Pd Mixed Nanoparticle Layer Based CO Sensors
Authors: Aruna I. , Kruis F. E.
Published: April 2011

This study reports a novel observation of the temperature dependent inversion in the CO sensitivity of the nanoparticle layers consisting of homogeneously mixed monodispersed Pd and SnO1.8 nanoparticles synthesized via aerosol route. Ability of sensing CO of as low as 10 ppb in dry synthetic air has been observed with decrease in nanoparticle size (to 5 nm) in the samples mixed with Pd nanoparticles, as compared to samples without Pd nanoparticles which show no sensitivity to CO in ppb levels. In contrast to the conductivity increase in SnO1.8 in response to CO exposure in the absence of Pd, the mixed nanoparticle layers exhibit decrease in conductivity. With increase in the operating temperature (523 to 673 K) reversal in the sensitivity has been observed at higher CO concentrations. The observed behavior can be understood in terms of the physiochemical and electronic processes.
Targeted Synthesis of Nanostructured Oxide Materials
Authors: Patzke Greta Ricarda , Zhou Ying
Published: April 2011

Morphology control is a key challenge in the straightforward hydrothermal production of technologically relevant anisotropic oxide materials. The use of readily available ionic additives as growth modifiers is discussed and compared for molybdenum- and tungsten oxide-based systems, and it is extended upon the formation of ternary W/Mo-oxides. Generally, the one-step hydrothermal synthesis of ternary and higher oxides is an important goal, because their properties often outperform those of the binary oxides. This holds especially for the Bi2O3-MoO3-VOx (BIMOVOx) system as a rich source of new materials. We present a new solution-based approach to α-Bi2O3 nanobelts starting from commercial Bi2O3 and K2SO4 as a key step on the way to anisotropic BIMOVOx-oxides. This hydrothermal process is an illustrative example of highly selective and efficient morphology control through an inorganic additive. As mechanistic and kinetic studies are crucial for the design of complex oxide nanomaterials, the Bi2O3-K2SO4 system is compared to our previous studies on Mo-, W- and V-oxides with respect to its hydrothermal parameter window and robustness.
Effect of Pore Morphology on the Electrochemical Properties of Electric Double Layer Carbon Cryogel Supercapacitors
Authors: Garcia Betzaida Batalla , Feaver Aaron M. , Champion Richard , Zhang Qifeng , Fister Tim T. , Nagle Kenneth P. , Seidler Gerald T. , Cao Guozhong
Published: April 2011

In this study a group of resorcinol-formaldehyde carbon cryogels (CC) have been processed chemically, via catalysis and activation, to obtain varied nanostructures and pore size distributions. To understand the relation between structure and electrochemical properties the capacitor can be studied as a dielectric system composed of a porous electrode and the electrolyte (Tetraethylammonium tetrafluoroborate in propylene carbonate). Using Electrochemical impedance spectroscopy (EIS) the complex capacitance and power are used to study the behavior of the system below the relaxation frequency fo (φ = −45°). Therefore, the relaxation of the capacitor system at the low frequency range, f < fo, may be used as a measure of pore/electrolyte interaction. The approach here proposed also allows for a direct experimental characterization of the capacitance and power at low frequencies where small pores are likely to affect the diffusion dynamics of the electrolyte molecules. The results suggest a correlation between the occurrence of small micropores and that of high power losses that are related to the resistive element produced at the low frequency range. Moreover, the impact of the micropore structure upon the supercapacitor's performance is apparent in its capacitance and energy as well. In addition to the complex power and capacitance other measurements including BET Nitrogen sorption, cyclic voltammetry, galvanic cycling and X-Ray Raman Scattering were used to characterize the samples and support these results.
The Role of Polymer-particle Interactions on the Viscoelastic Properties of Polymer Nanocomposites
Authors: Sarvestani Alireza , Jabbari Esmaiel
Published: April 2011

A molecular model is proposed for the dynamics of polymer chains in dilute polymer solutions containing well-dispersed spherical particles. In the presence of short range energetic affinity between the monomers and filler surface, the equilibrium structure of the adsorbed polymer layer is determined by a scaling theory. The viscoelastic response of the suspension is studied by a Maxwell model. It is shown that the solid-like properties of polymer nanocomposites in low frequency regimes could be attributed to the slowdown of the relaxation process of polymer chains. This process is controlled by the monomer-particle frictional interactions, density of the adsorbed polymer chains on the particles surface (controlled by monomer-particle adsorption energy), and volume fraction of the interfacial layer which can be enhanced by reduction of filler size or increasing the filler concentration.
Preparation of a Reduced Layered Tungstic Acid HxW2O7 via Acid Treatment of Bi2W2O9 in the Presence of Sn2+ Ions
Authors: Tahara Seiichi , Minato Takakazu , Kumada Nobuhiro , Hayashi Shigenobu , Sugahara Yoshiyuki
Published: April 2011

A reduced layered tungstic acid with a double-octahedral structure was prepared by acid treatment of an Aurivillius-type Bi2W2O9 in the presence of Sn2+ ions. While the color of the product formed by acid treatment with no Sn2+ ions present, H2W2O7, was yellow, a blue powder was obtained after the acid treatment in the presence of Sn2+ ions. No notable change in the morphology was observed after acid treatment. The X-ray diffraction pattern of the product acid-treated in the presence of Sn2+ ions was very similar to that of H2W2O7. Essentially all the Bi3+ ions were lost upon acid treatment, indicating the occurrence of selective leaching of bismuth oxide sheets in Bi2W2O9. A UV-visible absorption spectrum and XPS analysis demonstrated that the W6+ ions were partially reduced to W5+ ions, and the number of protons in the product was correspondingly 2.4 per [W2O7]. These results suggest the successful formation of a reduced layered tungstic acid, H2.4W2O7.
Photocatalytic Hydrogen Production from Gas-phase Methanol and Water with Nanocrystalline TiO2 Thin Films in High Vacuum
Authors: Noda Kei , Hattori Masashi , Amari Kouichi , Kobayashi Kei , Horiuchi Toshihisa , Matsushige Kazumi
Published: April 2011

Photocatalytic hydrogen production with gas-phase reactions in high vacuum was examined for nanocrystalline anatase-type titanium dioxide (TiO2) thin films. The hydrogen generation process on platinized TiO2 specimens was investigated using a quadrupole mass spectrometer at a real-time scale under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet ray (UV) illumination even in high vacuum (∼ 10−7 Torr). And the amount of produced H2 largely depends on the temperature of TiO2 samples, probably due to different surface states of TiO2. This study suggests the possibility of new high-speed H2 production system with gas-phase photocatalytic reactions.
Transport and Optical Characteristics of Al-rich AlO Film and its Application to a Non-volatile Memory
Authors: Nakata Shunji , Nagai Shingo , Kumeda Minoru , Kawae Takeshi , Morimoto Akiharu , Katagiri Yoshitada , Shimizu Tatsuo
Published: April 2011

We propose the new process for fabricating Al-rich Al2O3 thin film, which is used as a charge storage layer for non-volatile Al2O3 memory. Nanoscale Al-rich thin film is deposited using RF magnetron co-sputtering by setting an Al metal plate on an Al2O3 target. Al-rich Al2O3 shows a larger conduction current in I-V characteristics and larger optical absorption than stoichiometric Al2O3 due to the increased electron trap sites. The C-V characteristics of the Al-rich Al2O3 thin film show a large hysteresis window due to the charge trapping effect in the Al-rich structure.
Photoluminescence Quantum Yields from Crystalline and Amorphous Silicon Nanoparticles
Authors: Anthony Rebecca , Kortshagen Uwe
Published: April 2011

The optical properties of amorphous and crystalline silicon nanoparticles are studied. By tuning the power of the non-thermal plasma reactor, the structure of the particles is adjusted from amorphous to crystalline nanoparticles. The microstructure is studied using transmission electron microscopy, X-ray diffraction, and Raman vibrational spectroscopy. The photoluminescence quantum yields of crystalline nanoparticle samples are consistently higher than those of amorphous nanoparticles.
Tailoring of Structural Morphology of Silver Nanowires in Electrochemical Growth
Authors: Singh Amrita , Ghosh Arindam , Singh Amrita , Singh Amrita
Published: April 2011

Noble metal such as Ag normally exists in an fcc crystal structure. However as the size of the material is decreased to nanometer lengthscales, a structural transformation from that of its bulk state can be expected with new atomic arrangements due to competition between internal packing and minimization of surface energy. In many previous studies, it has been shown that silver nanowires (AGNWs) grown inside anodic alumina (AAO) templates by ac or dc electrochemical deposition from silver salts or complexes, adopt fcc structure and below some critical diameter ∼ 20 nm they may acquire hcp structure at low temperature. This is, however, critically dependant on the nature of confinement, as AgNWs grown inside nanotube confinement with subnanometer diameter have been reported to have fcc structure. Hence the question of the crystal structure of metal nanowires under combined influence of confinement, temperature and deposition condition remains open. In this abstract we show that the alternative crystal structures of AGNWs at room temperature can be achieved with electrochemical growth processes under specific conditions determined by the deposition parameters and nature of confinement. We fabricated AgNWs of 4H hexagonal structure with diameters 30 – 80 nm inside polycarbonate (PC) templates with a modified dc electrodeposition technique, where the nanowires were grown at deposition potentials as low as 10 mV in 2 M silver nitrate solution[1]. We call this low-potential electrodeposition (LPED) since the electrodeposition process occurs at potential much less than the standard Nernst potential (770 mV) of silver. Two types of electrodes were used – stainless steel and sputtered thin Pt film, neither of which had any influence on the crystal structure of the nanowires. EDS elemental analysis showed the nanowires to consist only of silver. Although the precise atomic dynamics during the LPED process is unclear at present, we investigated this with HRTEM (high-resolution transmission electron microscopy) characterization of nanowires grown over various deposition times, as well as electrical conductivity measurements. These experiments indicate that nanowire growth does not occur through a three-dimensional diffusion controlled process, as proposed for conventional over-potential deposition, but follow a novel instantaneous linear growth mechanism. Further experiments showed that, (a) conventional electrochemical growth at a small over-potential in a 2 mM AgNO3 solution yields nanowires with expected fcc structure inside the same PC templates, and (2) no nanowire was observed under the LPED conditions inside hard AAO templates, indicating that LPED-growth process, and hcp structure of the corresponding nanowires depend on deposition parameters, as well as nature of confinement.
Novel Synthesis of Metal Nanowhiskers: High-Temperature Glancing Angle Deposition
Authors: Suzuki Motofumi , Hamachi Kenji , Nagai Koji , Kita Ryo , Nakajima Kaoru , Kimura Kenji
Published: April 2011

We demonstrate high temperature glancing deposition (HT-GLAD) of metals on the heated substrate. It has been found that Al, Ag, Au, Fe nano-whiskers grow on the substrate of Si, SiO2, and glass substrates. The robustness in the selection of materials suggests that the HT-GLAD is a universal method to grow nano-whiskers of various metals. We also demonstrate the selective growth of the nano-whiskers on the substrate with micro-trench patterns. The metal nano-whiskers are useful for the nano electromechanical devices and vacuum microelectronics.
Pulsed PECVD Growth of Silicon Nanowires on Various Substrates
Authors: Parlevliet David , Cornish John C. L.
Published: April 2011

Silicon nanowires with high aspect ratio were grown using PPECVD and a gold catalyst on a variety of different substrates. The morphology of the nanowires was investigated for a range of crystalline silicon, glass, metal, ITO coated and amorphous silicon coated glass substrates. Deposition of the nanowires was carried out in a parallel plate PECVD chamber modified for PPECVD using a 1kHz square wave to modulate the 13.56MHz RF signal. Samples were analyzed using either a Phillips XL20 SEM of a ZEISS 1555 VP FESEM. The average diameter of the nanowires was found to be independent of the substrate used. The silicon nanowires would grow on all of the substrates tested, however the density varied greatly. It was found that nanowires grew with higher density on the ITO coated glass substrates rather than the uncoated glass substrates. Aligned nanowire growth was observed on polished copper substrates. Of all the substrates trialed, ITO coated aluminosilicate glass proved to be the most effective substrate for the growth of silicon nanowires.
Growth of SnO2-In2O3 Hetero Nanostructures
Authors: Kwon S. Joon , Hwang In-Sung , Kim Dong-Wan , Choi Young-Jin , Park Jae-Gwan
Published: April 2011

We present the formation of SnO2-In2O3 hetero nanostructures. Kinetically, SnO2 nanowires form prior to the heterostructure. In2O3shell was regularly distributed on the SnO2 nanowire surface, and form sheath subsequently. We theoretically explained the morphological evolution of an anisotropic heterostructure such as core-sheath structure.
Self-branching in GaN Nanowires Induced by a Novel Vapor-Liquid-Solid Mechanism
Authors: Nam Chang-Yong , Tham Douglas , Fischer John E.
Published: April 2011

Nanowires have great potential as building blocks for nanoscale electrical and optoelectronic devices. The difficulty in achieving functional and hierarchical nanowire structures poses an obstacle to realization of practical applications. While post-growth techniques such as fluidic alignment might be one solution, self-assembled structures during growth such as branches are promising for functional nanowire junction formation. In this study, we report vapor-liquid-solid (VLS) self-branching of GaN nanowires during AuPd-catalyzed chemical vapor deposition (CVD). This is distinct from branches grown by sequential catalyst seeding or vapor-solid (VS) mode. We present evidence for a VLS growth mechanism of GaN nanowires different from the well-established VLS growth of elemental wires. Here, Ga solubility in AuPd catalyst is limitless as suggested by a hypothetical pseudo-binary phase diagram, and the direct reaction between NH3 vapor and Ga in the liquid catalyst induce the nucleation and growth. The self-branching can be explained in the context of the proposed VLS scheme and migration of Ga-enriched AuPd liquid on Ga-stabilized polar surface of mother nanowires. This work is supported by DOE Grant No. DE-FG02-98ER45701.
Macroscopic 2D Design of Micro/Nano Grain Architectures by Laser Interference Metallurgy
Authors: Muecklich Frank , Gachot Carsten , Catrin Rodolphe , Schmid Ulrich , Lasagni Andrés
Published: April 2011

Tailoring of micro/nano structures and surface functionalization are key goals in surface processing of materials. A new technology for a unique geometric precise 2D micro/nano design of grain architectures is presented. By means of super lateral grain growth crystalline lattice patterns such as line-, dot- and cross-like patterns were generated. The grain dimensions may be selected between a few nanometers and about 10 micrometers. The phase and grain formation was characterized by Electron Backscatter Diffraction with regard to orientation distribution and texture formation. Furthermore, dynamic aspects of this laser induced recrystallization process are studied, such as the heat transport in the films, comparing the vertical with the lateral solidification velocities by two-dimensional finite element method (FEM) simulations. Finally, the mechanical properties of the tailored thin films have been determined using nanoindentation experiments.