bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Thermoelectric Properties of Ni-Cu based Alloy through Combinatorial Approach
Authors: Yamamoto Atsushi , Obara Haruhiko , Ueno Kazuo
Published: April 2011

The thermoelectric properties of Ni1-xCux (0<x<1) alloy are measured from 323K to 950K. The sample with optimized composition, Ni70Cu30 is found to possess large power factor value of 0.012 Wm−1K−2 at around 950K. Estimated figure of merit value ZT is 0.21 for Ni50Cu50 and 0.18 for Ni70Cu30 at the same temperature. A novel attempt of high-throughput parallel synthesis using multiple-wells is carried out to test the feasibility of combinatorial approach in this material system. The Seebeck coefficient is visualized over the multiple-wells combinatorial library and the other Ni-Cu composition-spread, and it is proved that further enhancement of throughput could be possible by conducting systematic experiments based on the combinatorial approaches performed in this study.
Thermoelectric and Mechanical Properties of Ca0.9Yb0.1MnO3 Based Materials
Authors: Kosuga Atsuko , Urata Saori , Funahashi Ryoji
Published: April 2011

The Ca0.9Yb0.1MnO3/Ag composites(the ratio of Ag to Ca0.9Yb0.1MnO3 was 0, 4.7, 9.4, and 18.8 wt %) were prepared by wet milling various amounts of Ca0.9Yb0.1MnO3 and Ag2O powder mixtures followed by sintering in order to improve the mechanical properties of Ca0.9Yb0.1MnO3 for n-type legs of thermoelectric oxide devices. The obtained composites consisted of two phases such as Ca0.9Yb0.1MnO3 and metallic silver from the X-ray diffraction (XRD) analysis. The scanning electron microscope (SEM) analysis indicated that the Ag particles, the size of which was within 5 μm, were homogeneously dispersed in Ca0.9Yb0.1MnO3 matrix for all the composites. The σf of 18.8 wt% Ag composite became 251 MPa, which was 2 times larger value than that of Ca0.9Yb0.1MnO3. The power factor (S2ρ) was slightly improved by the addition of silver particles. The maximum S2ρ, i.e. 0.26 mWm-1K-2 at 573 K was obtained for 18.8 wt% Ag composite.
Thermoelectric Properties and Magnetic Anisotropies of Magnetically Grain-Oriented Sr- or Bi-doped Ca3Co4O9 Thick Films
Authors: Horii Shigeru , Yamasaki Yuhya , Sakurai Masayuki , Funahashi Ryoji , Uchikoshi Tetsuo , Suzuki Tohru S , Sakka Yoshio , Ogino Hiraku , Shimoyama Jun-ichi , Kishio Kohji
Published: April 2011

We report magnetic properties of [Ca2CoO3-δ]0.62CoO2 (Ca349) powders with various average size and the Bi- and Sr-doping effects on thermoelectric properties for the magnetically grain-aligned and densified Ca349 thick films. Magnetic anisotropy at 300 K depended on the initial average size of Ca349 powders and decreased with the decrease in the size. This presumably suggests that distortion of crystal structure was induced by a ball-milling process and led to the change of magnetic anisotropy. On the Bi- and Sr-doping effects, an obvious enhancement of thermoelectric properties did not emerge in the case of the Sr-doping, whereas the enhancement was observed for the Bi-doped Ca349 thick films. However, a drastic decrease of magnetic anisotropy was caused by the Bi-doping. For usage of the p-type layer in multilayered thermoelectric module, tuning of the Bi-doping levels in which both enhancement of thermoelectric properties and a certain level of magnetic anisotropy are achieved is required.
Electrical Contact Fabrication and Measurements of Metals and Alloys to Thermoelectric Materials
Authors: D'Angelo Jonathan James , Timm Edward J , Ren Fei , Hall Bradley D , Case Eldon , Schock Harold , Kanatzidis Mercouri , Chung Duck Young , Hogan Timothy P
Published: April 2011

Low electrical contact resistance is essential for the fabrication of high efficiency thermoelectric generators in order to convert heat to electricity. These contacts must be stable to high temperatures and through thermal cycling. A ratio of the contact resistance to the leg resistance below 0.1 is the goal for fabrication of a high efficiency thermoelectric power generation device. Here we present the fabrication procedures and characterization of contacts of metal alloys to Pb-Sb-Ag-Te (LAST) and Pb-Sb-Ag-Sn-Te (LASTT) compounds. Contacts were fabricated and measured for both ingot and hot pressed materials. Stainless steel 316 has shown a low resistance contact to these thermoelectric materials when the proper bonding conditions are used. Different time-temperature-pressure conditions for bonding to n-type and to p-type legs are presented. Contact resistances below 10μΩcm2 have been measured. In addition, break tests have shown bond strengths exceeding the semiconductor fracture strength. One of the considerations used in selecting iron alloys for electrical interconnects is the similarity in the coefficient of thermal expansion to the LAST and LASTT materials which is 18 ppm/°C and relatively temperature insensitive. Contacts to the thermoelectric materials were accomplished by diffusion bonding in a furnace developed in our lab at Michigan State University. The furnace is capable of reaching temperatures of up to 1000°C with a controlled atmosphere of a reducing gas. Fabrication procedures and contact data are presented in this paper.
Kinetics of the remediation of Arsenic-contaminated groundwater using nanoscale magnetite particles
Authors: Hari Parameswar , Isley Aaron , Medders Greg , Purser Gordon
Published: April 2011

Arsenate species are toxic compounds widely found as contaminants in industrial and metallurgical environments. Environmental health problems related to industrial waste streams and related drinking water contaminations can commonly occur. Around the world, from Bangladeshi water wells to Oklahoman metal plating sites, toxic levels of arsenic (As) leach into potable water. This paper describes a flow loop system that relies on magnetic nanoscale particles, iron oxide (nanorust), for the removal of these toxic metals. The nanorust particles have an extremely high surface area which allows for the rapid removal of these metal oxides. Perhaps even more importantly, nanorust (iron oxide) also has the unique advantage that it can be easily removed and re-concentrated using inexpensive low field magnetic (125 T) separation techniques. In this study we will present results on treating low levels of As in water with nano particles of mesh size at 50 nm and 26 nm. Determination of As concentrations below 100 ppb level was attained using an Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) system and a continuous flow loop system.
EXPERIMENTAL OBSERVATIONS OF THE FAILURE MECHANISMS IN A BULK METALLIC GLASS COMPOSITE
Authors: Wang Hui , Bastawros Ashraf , Biner S. Bulent
Published: April 2011

The deformation and damage evolution behavior of a Ni-based bulk metallic glass composite reinforced with elongated brass phase is studied under cylindrical indentation. The estimated fracture toughness values based on the energy dissipation and the in-situ observation during the loading reveal the details of the damage evolution and toughening mechanisms in this composite system. The results indicate that the enhanced toughness of the BMG composite is plausibly an outcome of crack bridging mechanisms by the ductile brass phase, rather than a diffused array of nucleated shear bands in the hard BMG and arrest by the ductile reinforcing phase.
Nanometer-scale Structural Relaxation in Zr-based Bulk Metallic Glass
Authors: Hwang Jinwoo , Cao Hongbo , Voyles Paul M.
Published: April 2011

We investigated the influence of annealing on the nanometer-scale medium-range order in Zr54Cu38Al8 bulk metallic glass using fluctuation electron microscopy. Fluctuation microscopy experiments probing structure at a length scale of 1 nm show that the as-cast Zr bulk metallic glass contains significant medium range order. That structure is unchanged by annealing at 87% of the glass transition temperature for 24 hours, although that anneal does significantly change the differential scanning calorimetry trace.
Influence of Co Addition on Magnetic Properties and Glass Formation of Fe-based Amorphous Alloys
Authors: Piccin Rafael , Tiberto Paola , Lupu Nicoleta , Chiriac Horia , Baricco Marcello
Published: April 2011

In the present work, the influence of Co addition on the glass forming ability (GFA) and magnetic properties of the ((Fe1−xCox)75B20Si5)93Nb4Y3 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) alloy is evaluated. Ribbons and 1 mm diameter ingots were prepared by melt-spinning technique and Cu-mold injection casting technique, respectively. The presence of the amorphous phase was confirmed through X-ray diffraction and high temperature differential scanning calorimetry (HT-DSC). Rapid solidification leads to fully amorphous ribbons for all compositions. Conversely, ingots with Co content with x > 0.5 present boride crystalline phases.

Magnetization measurements were performed by means of vibration sample magnetometer in a temperature range from room temperature to 850 °C in order to determine the Curie temperature (TC) of the amorphous phase and to follow the formation of magnetic phases at high temperatures. In addition, hysteresis loops measurements were carried out to study the magnetic response of the samples. Co substitution until x = 0.5 is seen to simultaneously induce in the as cast ingots a decrease of coercive field from 52 to around 10 A/m and an increase of the Curie temperature of the amorphous phase from 480 to 700 K. A maximum saturation magnetization value of 123 emu/g was observed in the sample having x = 0.2. The role of Co substitution on glass formation is discussed on the basis of crystallization and melting behaviors, analyzed by HT-DSC. Magnetic properties are correlated with the presence of crystalline phases and their microstructures.
Preparation of Zr-based Metallic Glass Wire for Biomedical Application
Authors: Nagase Takeshi , Kinoshita Koichi , Umakoshi Yukichi
Published: April 2011

New Zr based metallic glass wires without bio-toxic elements of Ni, Al and Be were devel-oped for the further application as biomaterials by arc-melting type melt-extraction method. The continuous metallic glass wires with a good white luster and smooth surface were obtained in Zr-Ti-Al-Co, Zr-Al-Co-Cu, Zr-Al-Co and Zr-Ti-Co alloys. The Zr-based metallic glass wires show high tensile strength reaching 1000MPa. Furthermore, the wires exhibit good bending duc-tility and can be bent through 180 degrees without fracture. The Zr-based metallic glass wires achieve simultaneously high tensile strength, good bending ductility and high thermal stability.
Fracture Toughness Study on Zr-based Bulk Metallic Glasses
Authors: Suh Jin-yoo , Lind Mary Laura , Kim C. Paul , Conner R. Dale , Johnson William L
Published: April 2011

The fracture toughness of Zr-based bulk metallic glasses of various compositions was studied in the as-cast and annealed condition. Properties were characterized using x-ray and differential scanning calorimetry (DSC) and fracture surfaces were examined using electron microscopy (SEM). Quaternary Zr-Ti-Cu-Be alloys consistently had linear elastic fracture toughness values greater than 80 MPa·m1/2, while Vitreloy 1, a Zr-Ti-Cu-Ni-Be alloy, had an average fracture toughness of 48.5 MPa·m1/2 with a large amount of scatter. The addition of iron to Vitreloy 1 reduced the fracture toughness to 25 MPa·m1/2. Fracture surfaces were carefully analyzed using electron microscopy. Some samples had highly jagged patterns at the beginning stage of crack propagation, and the roughness of this jagged pattern correlated well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, were attributed to the formation of shear bands inside the sample. The Zr-Ti-Cu-Be alloy, having KQ=85 MPa·m1/2 as cast, was annealed at various time/temperature combinations. When the alloy was annealed 50°C below Tg, the fracture toughness dropped to 6 MPa·m1/2, while DSC and X-ray showed the alloy to still be amorphous. The roughness of the fracture surfaces on relaxed samples also compared well with the relative fracture toughness.
Indentation Response of Nanostructured Turfs
Authors: Zbib A. A. , Mesarovic S. Dj. , Bahr D. F. , Lilleodden E. T. , Jiao J. , McClain D.
Published: April 2011

When grown via chemical vapor deposition carbon nanotubes (CNTs) may take on the form of a “turf”, consisting of many CNTs with a complex interconnectedness attached to an inflexible substrate. These turfs can be formed over large areas and with a range of heights (between 1 to 100 μm), and grown on photolithographically patterned catalysts to form different aspect ratios. This study focuses on the indentation and permanent deformation of CNT assemblages under applied contact loading. Nanoindentation was conducted on CNT turfs and the properties, nominally the turf's elastic modulus and hardness, were 14.9 MPa ± 5.7 MPa and 2 MPa respectively. The onset of permanent deformation during indentation occurred at applied stresses of 2.5 MPa. The turf's collective permanent deformation under applied compressive loading was also studied. A model predicting the buckling stress of CNT turfs is also described.
Microstructural Investigation of the Deformation Zone below Nano-Indents in Copper
Authors: Rester Martin , Motz Christian , Pippan Reinhard
Published: April 2011

The deformation zone below nanoindents in copper single crystals with an <110>{111} orientation is investigated. Using a focused ion beam (FIB) system, cross-sections through the center of the indents were fabricated and subsequently analyzed by means of electron backscatter diffraction (EBSD) technique. Additionally, cross-sectional TEM foils were prepared and examined. Due to changes in the crystal orientation around and beneath the indentations, the plastically deformed zone can be visualized and related to the measured hardness values. Furthermore, the hardness data were analyzed using the Nix-Gao model where a linear relationship was found for H2 vs. 1/hc, but with different slopes for large and shallow indentations. The measured orientation maps indicate that this behavior is presumably caused by a change in the deformation mechanism. On the basis of possible dislocation arrangements, two models are suggested and compared to the experimental findings. The model presented for large imprints is based on dislocation pile-ups similar to the Hall-Petch effect, while the model for shallow indentations uses far-reaching dislocation loops to accommodate the shape change of the imprint.
Measurement of Ultrathin Film Mechanical Properties by Integrated Nano-scratch/indentation Approach
Authors: Bastawros Ashraf , Che Wei , Chandra Abhijit
Published: April 2011

The thickness and property measurements of thin films on a substrate are crucial for a wide range of applications. Classical techniques have relied on various physical properties to identify film thickness, independent of its mechanical properties. Here, a new experimental technique is devised to evaluate the film thickness, its stiffness and its flow stress. The technique utilizes the variation of the measured apparent modulus of a ductile film on a substrate from a nano-indentation experiment, in conjunction with the measured normal and tangential forces and the scratch depth in a nano-scratch experiment. These combined measurements are calibrated through a simple statically admissible model to yield the unknown quantities. The measurements reasonably agree with the finite element predictions and are ascertained by XPS film thickness measurements. The technique is applied to study the formed oxide nano-layer during copper chemical mechanical planarization process.
Reverse Plasticity in Nanoindentation
Authors: Huang Yongjiang , Tjahyono Nursiani Indah , Shen Jun , Chiu Yu Lung
Published: April 2011

This paper summarises our recent cyclic nanoindentation experiment studies on a range of materials including single crystal and nanocrystalline copper, single crystal aluminium and bulk metallic glasses with different glass transition temperatures. The unloading and reloading processes of the nanoindentation curves have been analysed. The reverse plasticity will be discussed in the context of plastic deformation mechanisms involved. The effect of loading rates on the mechanical properties of materials upon cyclic loading will also be discussed.
Martensite Transition and Microscopic Magnetism of Epitaxial Ni2MnGa Films
Authors: Jakob Gerhard , Eichhorn Tobias , Kallmayer Michael , Elmers Hans-Joachim
Published: April 2011

A magnetically induced shape memory effect in Ni2MnGa results in huge magnetostrictive effects of several percent. Using x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) we investigated element specific magnetic moments and electronic structure of single crystalline, (110) oriented Ni2MnGa films on a-plane Al2O3 substrates in the austenite and martensite state. The structural phase transition of the samples is evident from temperature dependent x-ray diffraction and magnetization measurements. The Ni XAS differ significantly for temperatures above and below the martensite transition in agreement with published ab-initio calculations. Using XAS in transmission geometry on our thin film samples we observe the corresponding reduction of the absorption feature as predicted by theoretical calculations. The XMCD analysis shows the orbital contribution of the Ni electrons to be responsible for the magnetic anisotropy.
Effect of Surface Oxide Layer on Mechanical Properties of Single Crystalline Silicon
Authors: Miyamoto Kenji , Sugano Koji , Tsuchiya Toshiyuki , Tabata Osamu
Published: April 2011

Fatigue fracture under cyclic loading of single crystal silicon (SCS) is concerned and fatigue properties and mechanism are investigated widely. Surface oxide is considered to have an important role on fatigue fractures. In this paper, the tensile testing of SCS whose surface was intentionally oxidized and the effect of the oxide thickness on the mechanical properties were reported. After fabrication of SCS specimens, they were oxidized in dry oxidization at 1100 ºC. Quasi-static tensile testing of SCS specimens with no, 100-nm-oxide, and 200-nm-oxide thick oxide was performed. As the results, the deviation in fracture strain was decreased by oxidation, and the fracture origin was observed to be the inner silicon part. These results might be caused by the decrease of surface roughness and defects formation by oxygen precipitation during thermal oxidation.
C-Axis Oriented ZnO Film by RF Sputtering and its Integration with MEMS Processing
Authors: Chandra Sudhir , Singh Ravindra
Published: April 2011

In the present work, we report a new fabrication process to integrate the “c-axis oriented” ZnO films with bulk-micromachined silicon diaphragms. ZnO films are very sensitive to the chemicals used in the micro-electro-mechanical systems (MEMS) fabrication process which include acids, bases and etchants of different material layers (e.g. SiO2, chromium, gold etc.). A Si3N4 layer is incorporated to protect the ZnO film from the etchants of chromium and gold used for patterning the electrodes. A mechanical jig is used for protecting the front side (ZnO film side) of the wafer from ethylenediamine pyrocatechol water (EPW) during the anisotropic etching of silicon. The resistivity measurement performed on the ZnO film integrated with micro-diaphragm shows the reliability of the fabrication process proposed in this work.
Compressive Stress Accumulation in Composite Nanoporous Gold and Silicone Bilayer Membranes: Underlying Mechanisms and Remedies
Authors: Seker Erkin , Huang Ling , Begley Matthew R. , Bart-Smith Hilary , Kelly Robert G. , Zangari Giovanni , Reed Michael L. , Utz Marcel
Published: April 2011

This paper outlines a simple method to fabricate a bilayer membrane consisting of a thin nanoporous gold layer infused with uncured polydimethylsiloxane. The fabrication technique offers excellent adhesion due to mechanical interlocking between porous layer and elastomer, and excellent electrical conductivity up to 25% strain, despite a very low effective elastic modulus (∼1.35 MPa) due to cracks in the embedded gold layer. Initially freestanding circular membranes displayed significant out of plane buckling, and created difficulties in extraction of membrane mechanical properties. The underlying mechanisms of compressive stress accumulation that lead to membrane buckling and remedies to prevent it are discussed.
Micro-Topography Enhances Directional Myogenic Differentiation of Skeletal Precursor Cells
Authors: Zhao Yi
Published: April 2011

Skeletal muscle tissues were constructed using an in vitro model, by differentiating skeletal myoblasts using an array of linear microstructures with the medium aspect ratios. The adaptation of skeletal myoblasts has been characterized with immunoflurescence microscopy during cell proliferation and differentiation. In particular, the dependence of the alignment efficiency on the dimensions of the microstructures was studied. The morphology difference of the myotubes in the three-dimensional tissues was reported. This paper holds the promise of efficient on-chip fabrication of skeletal muscle tissues and has an important implication in direct muscle repair and muscular mechanics.
Relative Resistance Chemical Sensors Built on Microhotplate Platforms
Authors: Hertz Joshua L. , Montgomery Christopher B. , Lahr David L. , Semancik Steve
Published: April 2011

The selectivity, sensitivity, and speed of metal oxide conductometric chemical sensors can be improved by integrating them onto micromachined, thermally-controlled platforms (i.e., microhotplates). The improvements largely arise from the richness of signal inherent in arrays of multiple sensing materials and the ability to rapidly pulse and collect data at multiple temperatures. Unfortunately, like their macroscopic counterparts, these sensors can suffer from a lack of repeatability from sample-to-sample and even run-to-run. Here we report on a method to reduce signal drift and increase repeatability that is easily integrated with microhotplate chemical sensors. The method involves passivating one of a pair of identically-formed sensors by coating it with a highly electrically resistive and chemically impermeable film. Relative resistance measurements between the active and passive members of a pair then provide a signal that is reasonably constant over time despite electrical, thermal and gas flow rate fluctuations. Common modes of signal drift, such as microstructural changes within the sensing film, are also removed. The method is demonstrated using SnO2 and TiO2 microhotplate gas sensors, with a thin Al2O3 film forming the passivation layer. It is shown that methanol and acetone at concentrations of 1 µmol/mol, and possibly lower, are sensed with high reproducibility.
Fabrication of C54-TiSi2 Thin Films Using Cathodic Arc Deposition and Rapid Thermal Annealing
Authors: Xia Hui , Knudsen William R. , Bergstrom Paul L.
Published: April 2011

Due to its low electrical resistivity and high thermal stability, C54-TiSi2 thin films can be used in some MEMS application, such as RF MEMS, to reduce RC delay and improve dynamic performance. In this paper, TiSi2 thin films have been prepared for the first time by using cathodic arc deposition to study the impact of energetic ion bombardment on the film microstructure and subsequent C49-C54 phase transformation during annealing. TiSi2 compound was used as the cathode and a substrate bias was varied to control kinetic energy of the ions during the film growth. Rutherford backscattering spectrometry and transmission electron microscopy were utilized to characterize the film composition and microstructure. The composition of the resultant TiSix thin films varies from x=2.4 to x=1.4 when the substrate bias was varied from floating to –200V. The as-deposited TiSix films are amorphous under no substrate heating and a phase separation at nano scale with inhomogeneous distribution of Ti and Si atoms was observed within the amorphous phase. Si atoms are seen to segregate on the boundary of Ti-rich domains and the domain size increased with the substrate bias. For a 90nm-thick TiSi2 film deposited on a SiO2/Si substrate, kinetics of the C49-C54 phase transformation was studied by measuring the change of film resistivity upon rapid thermal annealing. It was found that the C49-C54 phase transition temperature is higher (>900°C) for the arc-deposited TiSi2 thin films compared to evaporated and sputtered films and the activation energy for the transformation was calculated to be 6.1±0.2eV.
Compressive magnetostriction of FeSm alloy film
Authors: Nakano Ryo , Matsumura Yoshihito , Nishi Yoshitake
Published: April 2011

The compressive magnetostriction values of Fe2.4Sm alloy thin film prepared on silicon, copper and titanium substrates (300μm thickness) by direct current magnetron sputtering process were investigated. When the residual gas pressure before argon sputtering and the sputtering pressure of argon gas (5 N) were below 3.2×10−4 Pa and 2.0×10−1 Pa, respectively, the thickness of the Fe2.4Sm films deposited was about 3 μm. Compressive magnetostriction of Fe2.4Sm alloy film on titanium sheet generates the large bending motion, rather than those on silicon wafer and copper substrates. The high magnetostrictive susceptibility of the films was observed at low magnetic field.
Nature-Inspired Microfluidic Manipulation Using Magnetic Actuators
Authors: Khaderi S. N. , Ioan D. , den Toonder J. M. J. , Onck P. R.
Published: April 2011

Magnetically actuated micro-actuators are proposed to propel and manipulate fluid in micro-channels. As the fluid flows at low Reynolds number in such systems, the actuator should move in an asymmetric manner. The proposed actuators are polymer films with embedded magnetic particles, which are actuated by an external magnetic field. Based on the nature of the particles, the films can be either ferromagnetic or super-paramagnetic. We have identified four configurations in which the actuator exhibits an asymmetric motion.
Phonon Interaction in InGaAs/GaAs Quantum Dots
Authors: Werner Stefan , Zimmer Patrick , Strittmatter André , Hoffmann Axel
Published: April 2011

The carrier-phonon interaction in self-organized In(Ga)As/GaAs quantum dots is investigated under resonant excitation of the ground-state transition. Different phonon-coupled processes are observed. The distinction between Raman scattering and hot-luminescence process has been resolved by time-dependent photoluminescence measurements. The quantum dot LO (33.8 meV) as well as an interface (36.5 meV) phonon mode is observed by resonant Raman scattering. For the QD LO phonon mode, a very short radiative lifetime of 10 ps was found.
Fabrication of SERS Active Substrates by Nanoimprint Lithography
Authors: Li Kebin , Cui Bo , Clime Liviu , Veres Teodor
Published: April 2011

A method for low-cost fabrication of SERS substrates in rapid and reproducible way based on nanoimprint lithography (NIL) method has been developed. The SERS enhancement for detection of Rhodamine 6G molecules is demonstrated on two model nanostructures comprising either Au nano-crescents or Ag nano-wells fabricated by this method. Numerical simulations based on discrete dipole approximation (DDA) method show that the observed enhancement of the SERS signal for the given geometries originates in hot-spots localized at the tips of the nanocrescent. For the nanowell, the hotspots are mainly localized inside the cavity, on the side of the nanodonut, or at the edge of the bottom nanodisc when it is excited by a laser at the wavelength of 785 nm.
VUV-photon Induced Formation of Hydrophilic and Hydrophobic Micro Domains Structure on Intraocular Lens Surface for Blocking after Cataract
Authors: Sato Yuji , Kawai Kenji , Sasoh Mikio , Ozaki Hiroaki , Ohki Takeo , Shiota Hiroshi , Murahara Masataka
Published: April 2011

A micro domain structure, which hydrophilic and hydrophobic groups were arrayed alternately, was formed on the surface of an intraocular lens [IOL] by using ultra violet rays [VUV]. With this technique, the IOL that is free from fibrin has been developed. In order to substitute the hydrophilic groups in matrix-form on the surface, an ArF laser light was then irradiated on the hydrophobic surface in the presence of water for the −OH groups, through the 50-micrometer dot-patterned reticle. With this selective photochemical surface modification, the hydrophilic and hydrophobic groups were arrayed alternately on the sample surface. The modified IOL was soaked in 0.1-wt % fibrin solutions, and the fibrin-sticking rate was measured by using an infrared spectroscopy [FT-IR]. It results that the absorption coefficient of amide band reached to 0.0006, decreasing to one-six of non-treatment sample's.
Self-Organization and Nanocluster Formation Processes in Nonlinear Molecular Chains
Authors: Tereshko I. , Abidzina V. , Elkin I. , Kalinowskaya N. , Melnikau I.
Published: April 2011

The goal of this work is to investigate self-organization processes in molecular chains. Computer simulation has been performed by means of a molecular dynamics method. Morse potential was chosen as the potential of atomic interaction. Molecular chains were exposed to low-energy ion impact by two means: mono beam and plasma treatment. The amount of the energy transferred to molecules of the chain was varied in wide range but it must be less than the energy needed to break the chain. Chains with water molecules that were cut from microcrystal of ice (homogeneous chains) as well as net of hydrogen bonds (heterogeneous chains) were under our investigations. In last case areas with periodical structure symbolize embedded crystal nanoclusters in the whole disordered medium.

We showed that nonlinear oscillations become excited in the chains after low-energy ion impact and as a result of them molecules become stabilized in new positions, which results in the formation and development of new metastable molecular groups (nanoclusters). In homogenous chains formed nanoclusters correspond to elements of “molecular memory”. We showed that in homogeneous molecular chains critical energy needed for self-organization processes development is less than for nonlinear molecular chains with already embedded clusters. In this case nanocluster becomes an active zone which determines further self-organization processes. It is clusters that provide new complexes of physical and chemical properties. This computer model can be also used for simulation of low-energy ion impact on polymers and biological objects.
Carbon Nanospheres: “Green” Synthesis, Characterization, and Growth Kinetics
Authors: Doorley Mathilda , Mishra Sanjay R , Laradji Mohamad , Gupta Ram K , Ghosh Kartik
Published: April 2011

An attempt is made to understand the growth kinetics of carbon nanospheres (CNS) synthesized using a “green” technique. An aqueous solution of glucose, the precursor, was hydrothermally treated to produce porous CNS with homogeneous size distribution and smooth surfaces. The growth of CNS was studied by evaluating transmission electron microscope images as a function of hydrothermal reaction time and temperatures. Raman spectra revealed the presence of short-ordered graphitic nanostructures in an amorphous carbon matrix. FTIR spectroscopy confirms the carbonization of glucose and shows the presence of surface hydroxyl groups on CNSs. Based on various experimental observations it is proposed that the growth of CNSs is dictated by a reaction-controlled mechanism where long chain glucose-based oligomers bond to the CNS surface. The narrow size distribution and highly hydrophilic surface of these amorphous CNS makes them potential candidates for biomedical applications.
Enlarging the Bandwidth of Nano-scale Propagating Plasmonic Modes in Deep-subwavelength Cylindrical Holes
Authors: Catrysse Peter B. , Fan Shanhui
Published: April 2011

Subwavelength cylindrical holes in optically thick metallic films always support a propagating HE11 mode near the surface plasmon frequency, regardless of how small the holes are. For holes filled with a uniform dielectric material, the bandwidth of the HE11 mode asymptotically approaches zero as the hole size is reduced to deep-subwavelength scales. We show that it is possible to create nano-scale propagating plasmonic modes with very large bandwidth in holes that are concentrically filled with two different dielectric materials, even when the hole radius goes to zero.
Surface Plasmon Structures for Surface-Enhanced Raman Scattering
Authors: Khan Muhammad Ajmal , Huang He , Shanker B. , Hogan Timothy P.
Published: April 2011

Surface-enhanced Raman scattering (SERS) can enhance the intensity of Raman radiation by many orders of magnitude for molecules bound to metallic nanostructures. SERS is generally thought to have been a result of excitation of surface plasmons in nanostructured metal, which greatly enhances local electric field experienced by the molecule. Common SERS substrates fabricated using noble metal colloidal or electrochemically roughened thin films suffer from lack of homogeneity where only few hot spots yield high enhancement. We explore semiconducting nanowires and metallic nanorods as an economical, stable, and uniform SERS substrate for the detection of trace amount of chemicals and bio-species. We utilize bulk synthesized semiconducting nanowires as nano-scale structures that can be coated with noble metals or their colloidal forms to allow for excitation of surface plasmons over broad frequency range. The use of nanowires as SERS substrates has several advantages. The surface properties of these nanowires are highly reproducible and well defined as compared to other systems like colloidal aggregates, electrochemical roughening etc. The synthesized nanowires offer many unique features (sharp vertices, noncircular cross-sections, inter-wire coupling) that may lead to larger field enhancement factors. High density of nanowires means close interaction between adjacent nanowires, which enables SERS to manifest for a broad selection of excitation sources. We have synthesized germanium dioxide and zinc oxide nanowires using the vapor-liquid-solid growth mechanism utilizing a simple quartz tube furnace set up. The nanowires are grown either using thin gold film (5-15 nm) or colloidal gold (20 nm or 60 nm) as catalyst on substrates of silicon, quartz, and alumina. The resulting nanowires are dense (100-300 nm diameter, 10-40 μm long) and randomly distributed on the substrate. The nanowires are subsequently coated with thin films (10-15 nm) of gold that provide plasmons active surface. We have also investigated silver nanorods on glass formed by grazing angle deposition using e-beam evaporation. These nanorods have a diameter of ∼ 50-70 nm with lengths averaging 300-400 nm. These well aligned high aspect ratio and dense structures are ideal for excitation of surface plasmons. The synthesized structures have been characterized using SEM, TEM, and EDS. The SERS studies were conducted using EzRaman-L system from Enwave Optronics, Inc. Silver nanorods and gold-coated nanowires have been found to exhibit significant Raman enhancement for micro-molar concentrations of Rhodamine 6G and Nile blue, and are promising candidates for SERS applications.
Geometrical Study on Change of Pore Volume of MCM-41 Functionalized with Aminopropyl Groups
Authors: Murakami Kenji , Fuda Kiyoshi , Sugai Mikio
Published: April 2011

Mesoporous silicas functionalized with aminopropyl groups were synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxysilane (APTES) and characterized by nitrogen adsorption-desorption measurements. The pore volume drastically decreased from about 900 mm3/g for the unfunctionalized mesoporous silica to about 300 mm3/g for the aminopropyl-functionalized mesoporous silica (1.65 mmol-NH2/g). This result was explained in terms of the surface density of the aminopropyl groups in the pore.
Plasma Torch Production of Ti-Al Nanoparticles
Authors: Phillips Jonathan , Cheng Lili , Luhrs Claudia , Zea Hugo , Courtney Matthew , Hanson Caleb
Published: April 2011

Using the Aerosol-through-Plasma (A-T-P) technique high surface area (from 100 to 203 m2/gm) bi-cationic (Ti-Al) oxide particles of a range of stoichiometries were produced that showed remarkable resistance to sintering. Specifically, we found that homogeneous nanoparticles with surface areas greater than 150 m2/gm were produced at all stoichiometries. In particular, for particles with a Ti:Al ratio of 1:3 a surface area of just over 200 m2/gm was measured using the BET method. The most significant characteristic of these particles was that their sinter resistance was far superior to that of TiAl particles produced using any other method. For example, A-T-P generated particles retained >70% of their surface area even after sintering at 1000 C for five hours. In contrast, particles made using all other methods lost virtually all of their surface area after an 800 C treatment.
Tridimensional Microstructures of C-SWNT Reinforced Polymer Nanocomposite by Means of a Microfluidic Infiltration Approach
Authors: Lebel Louis Laberge , Aissa Brahim , Khakani My Ali El , Therriault Daniel
Published: April 2011

Three-dimensional (3D) microstructures of single walled carbon nanotube (C-SWNT)/polymer nanocomposite are fabricated by the infiltration of 3D microfluidic networks. The microfluidic network was first fabricated by direct-write assembly which consists of the robotised deposition of fugitive ink filaments on an epoxy substrate to form a 3D microstructured network. After encapsulation of the deposited structure with an epoxy resin, the fugitive ink was removed by heating, resulting in a 3D network of microchannels. This microfluidic network is then infiltrated by a ultraviolet (UV) -curable polymer loaded with C-SWNTs. The C-SWNTs were produced by the UV-laser ablation method, physico-chemically purified and dispersed in a polymer matrix using ultrasonic treatment in dichloromethane. The C-SWNTs were characterized by means of high-resolution scanning electron microscopy and microRaman spectroscopy. The infiltrated nanocomposite (i.e., the C-SWNT reinforced polymer) is then cured under UV exposure and post-cured. The manufactured 3D microstructures were rectangular sandwich beams having an epoxy core and unidirectional nanocomposite fibers placed parallel to the beam axis, on both sides of the core. Flexural mechanical tests were performed on empty, pure resin and nanocomposite microfluidic beams using a dynamic mechanical analyzer. The achieved nanocomposite beams were found to show an increase of 5% in the storage modulus and more than 50% increase in the loss modulus, under 30°C compared to the pure resin beams. The nanocomposite infiltration of microfluidic networks is shown to be a promising approach to achieve 3D microstructures of reinforced nanocomposites.
Effect of Functionalization on the Crystallization Behavior of MWNT-PBT Nanocomposites
Authors: Mago Gaurav , Velasco-Santos Carlos , Martinez-Hernandez Ana L. , Kalyon Dilhan M. , Fisher Frank T.
Published: April 2011

There is tremendous interest in using low loadings of multiwalled carbon nanotubes (MWNTs) to enhance the multifunctional properties of polymers, with functionalization often pursued to increase the dispersion and effective reinforcement of MWNTs within the polymer. In our interest to understand the effect of MWNT functionalization on Poly (butylene terephthalate) (PBT) crystallization kinetics, morphology and mechanical properties, nanocomposites were fabricated with both as-received and carboxyl group (-COOH) functionalized MWNTs. Initial results indicate as-received and functionalized nanotubes alter the crystallization temperature and crystal size for quiescent samples. In addition, isothermal crystallization studies using an Advanced Rheometric Expansion System (ARES) show that the addition of MWNTs increases the rate of PBT crystallization. However, functionalization was found to decrease the rate of nanocomposite crystallization as compared to nanocomposites samples prepared using pristine MWNTs, suggesting that nanotube functionalization weakens the nucleation effect observed in the nanocomposite samples. These results suggest that semicrystalline polymer nanocomposite crystallization kinetics and morphology can be significantly influenced by nanoparticle functionalization and chemistry. Further study of how these changes impact the rheological and multifunctional properties of semicrystalline nanocomposite systems are ongoing.
Nano-dispersed Particulate Ceramics in Poly-Lactide-Co-Glycolide Composites Improve Implantable Bone Substitute Properties
Authors: Liu Huinan , Webster Thomas J.
Published: April 2011

Metallic materials widely used in orthopedic applications have much stronger mechanical properties (such as elastic modulus) than natural bone, which can weaken the newly formed bone interface due to stress-shielding. Because natural bone is under continuous physiological stresses (such as compression, tension, torsion, and/or bending), the mechanical properties of orthopedic implant materials should closely match those of living bone. This is necessary to minimize stress and strain imbalances during physiological loading conditions which will lead to implant failure. The objective of the present study was to characterize the mechanical properties of PLGA with well-dispersed nanophase titania. The dispersion of titania in PLGA was controlled by sonication and was characterized by field emission scanning electron microscopy and image analysis. For this purpose, two major stresses (compression and tension) that natural bone experiences under physiological loading conditions were characterized using an Instron Material Testing System. The results showed that nano-dispersed titania particles in PLGA increased the compressive and tensile modulus of such scaffolds compared to pure PLGA scaffolds and the more agglomerated ceramics in PLGA scaffolds. The mechanisms behind these results were also speculated. Since the predominant feature of nano-particles lies in their ultra-fine dimension, a large fraction of filler atoms can reside at the PLGA-ceramic interface which can lead to a stronger interfacial interaction, but only if the nano-particles are well dispersed at the nanometer level in the surrounding polymer matrix. As the interfacial PLGA-ceramic structure plays a critical role in determining the mechanical properties of composites, nano-composites with a great number of smaller interfaces could be expected to provide unusual properties, and the shortcomings induced by the heterogeneity of conventional (or micron) particle filled composites would also be avoided. Therefore, coupled with prior studies demonstrating greater osteoblast functions, the combination of PLGA with a strong and biocompatible well-dispersed nano-ceramic phase may provide better candidate materials for orthopedic applications.
Growth and Characterization of a Combinatorial Array of Mixed-Phase Magnesium-Aluminum Thin-Film Alloys
Authors: Olk Charles , Haddad Daad B.
Published: April 2011

Combinatorial gradient-controlled sputter deposition has been employed to produce a library of 100 separate thin films with a wide range of Mg-Al alloy compositions. We have successfully isolated the â (Mg17Al12) phase in polycrystalline films for investigation. The presence of the â phase has been found to be desirable for increasing corrosion resistance; however, in structural components under tensile loading and/or at elevated temperatures, the â phase precipitates undergo coarsening which induces poor creep behavior in several common alloys. We have also synthesized amorphous Mg-Al and mixed-phase compositions as identified by X-ray diffraction measurements. Details of the growth procedure as well as structural and compositional characterization are presented.
Investigation of Phase Transition in Stacked Ge-Chalcogenide/SnTe Phase-change Memory Films
Authors: Bai Feiming , Gupta Surendra , Devasia Archana , Kurinec Santosh , Davis Morgan , Campbell Kris A
Published: April 2011

Phase transitions in stacked GeTe/SnTe and Ge2Se3/SnTe thin layers for potential phase-change memory applications have been investigated by X-ray diffraction using a two-dimensional area detector system. The as-deposited underlying GeTe or Ge2Se3 layer is amorphous, whereas the top SnTe layer is crystalline. In the GeTe/SnTe stack, the crystallization of GeTe phase occurs near 170°C, and upon further heating, the GeTe phase disappears, followed by the formation of rocksalt-structured GexSn1−xTe solid solution. In the Ge2Se3/SnTe stack, the phase transition starts with the separation of a SnSe phase due to the migration of Sn ions into the Ge2Se3 layer. SnSe is believed to facilitate the crystallization of Ge2Se3-SnTe solid solution at ∼360°C, which is much lower than the crystallization temperature of Ge2Se3, therefore consuming less power during the phase transition.
Polymer Composites with Oriented Magnetic Nanowires as Fillers
Authors: Sun Li , Keshoju Kusuma
Published: April 2011

Metallic nickel nanowires with excellent physical properties have been introduced into polydimethylsiloxane matrix to form polymer nanocomposites. Nanowires were synthesized by template-assisted electrochemical deposition. By utilizing ferromagnetic nickel nanowires, small external magnetic field can be used to control their alignment and distribution during composite synthesis. Unlike dielectrophoresis, optical tweezers, and microfluidic flow control, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. Polydimethylsiloxane composites with nanowires arranged in longitudinal, transverse, and random orientations with respect to the applied load direction were studied. Tensile tests showed that the composites with longitudinal arrangement have higher elastic modulus and tensile strength than the other composite samples. Experimentally obtained elastic modulus values were compared with the prediction of classical Halpin-Tsai model. Metallic nickel nanowires with excellent physical properties have been introduced into polydimethylsiloxane matrix to form polymer nanocomposites. Nanowires were synthesized by template-assisted electrochemical deposition. By utilizing ferromagnetic nickel nanowires, small external magnetic field can be used to control their alignment and distribution during composite synthesis. Unlike dielectrophoresis, optical tweezers, and microfluidic flow control, magnetic manipulation provides a cost-effective, non-contact, and versatile approach to control nanostructured materials in fluids over a large area. Polydimethylsiloxane composites with nanowires arranged in longitudinal, transverse, and random orientations with respect to the applied load direction were studied. Tensile tests showed that the composites with longitudinal arrangement have higher elastic modulus and tensile strength than the other composite samples. Experimentally obtained elastic modulus values were compared with the prediction of classical Halpin-Tsai model.