bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Characterization of High Aspect Ratio Silicon Nanolines
Authors: Huang Huai , Huang Huai , Zhao Qiu , Luo Zhiquan , Im Jang-Hi , Ho Paul S , Kang Min Kyoo , Huang Rui , Cresswell Michael W 
Published: April 2011

AbstractIn this study, we performed nanoindentation experiments on two sets of silicon nanolines (SiNLs) of widths 24 nm and 90 nm, respectively, to investigate the mechanical behavior of silicon structures at tens of nanometer scale. The high height-to-width aspect ratio (∼15) SiNLs were fabricated by an anisotropic wet etching (AWE) method, having straight and nearly atomically flat sidewalls. In the test, buckling instability was observed at a critical load, which was fully recoverable upon unloading. It was found that friction at the contact between the indenter and SiNLs played an important role in the buckling response. Based on a finite element model (FEM), the friction coefficient was estimated to be in a range of 0.02 to 0.05. The strain to failure was estimated to range from 3.8% for 90 nm lines to 7.5% for 24 nm lines.
The Growth and Mechanical Properties of Gold Nanowires
Authors: Dou Rui , Derby Brian 
Published: April 2011

AbstractWe have measured the yield strength of gold nanowire forests with mean diameter 30, 60 and 70 nm fabricated by electro-deposition into porous alumina templates. All nanowire sizes showed yield strengths much greater than expected from polycrystalline gold specimens with the 30 nm specimens having a yield stress in excess of 1.4 GPa. We found no significant work hardening at plastic strains up to 30%. The strength of the nanowires as a function of wire diameter follows the same trend as has been reported for the compression strength of larger gold pillars reported in the literature. TEM observations of deformed wires are consistent with mechanisms of dislocation induced deformation.
Growth and Optical Properties of SnO2 Ultra-Small Nanorods by the Novel Micelle Techniques
Authors: Rath Satchidananda , Nozaki Shinji , Ono Hiroshi , Uchida Kazuo , Khojima Satoshi 
Published: April 2011

AbstractTin-dioxide (SnO2) ultra-small nanorods (UNR) have been successfully synthesized using the novel micellar technique. From transmission electron microscopy, the average diameter and length of the UNRs are estimated to be 1.3 nm and 5.0 nm, respectively. The crystal structure of the SnO2 UNRs was found to be tetragonal from the glazing incidence x-ray diffraction. The optical band gap estimated from the absorption spectrum is blue-shifted by 1 eV from that of bulk (3.64 eV). The photoluminescence spectrum shows two groups of peaks each with several fine peaks, one in the wavelength range of 270 – 370 nm and the other in the range of 380 – 500 nm which are due to the strong quantum confinement effect.
Engineering the shape of Zinc Oxide crystals via sonochemical or hydrothermal solution-based methods
Authors: Palumbo Marco , Henley Simon J. , Lutz Thierry , Stolojan Vlad , Cox David , Silva S. Ravi P. 
Published: April 2011

AbstractRecent results in the use of Zinc Oxide (ZnO) nano/submicron crystals in fields as diverse as sensors, UV lasers, solar cells, piezoelectric nanogenerators and light emitting devices have reinvigorated the interest of the scientific community in this material. To fully exploit the wide range of properties offered by ZnO, a good understanding of the crystal growth mechanism and related defects chemistry is necessary. However, a full picture of the interrelation between defects, processing and properties has not yet been completed, especially for the ZnO nanostructures that are now being synthesized. Furthermore, achieving good control in the shape of the crystal is also a very desirable feature based on the strong correlation there is between shape and properties in nanoscale materials. In this paper, the synthesis of ZnO nanostructures via two alternative aqueous solution methods - sonochemical and hydrothermal - will be presented, together with the influence that the addition of citric anions or variations in the concentration of the initial reactants have on the ZnO crystals shape. Foreseen applications might be in the field of sensors, transparent conductors and large area electronics possibly via ink-jet printing techniques or self-assembly methods.
Effect of interfacial strain on shape and composition of MOCVD grown III-Nitride nanostructures
Authors: Jindal Vibhu , Grandusky James , Tripathi Neeraj , Tungare Mihir , Shahedipour-Sandvik Fatemeh 
Published: April 2011

AbstractIt is determined that the interfacial strain due to lattice mismatch between the substrate (template) and the overgrown nanostructure has substantial influence on the final morphology and faceting of nanostructures. AlGaN and GaN nanostructures were grown on different substrates/templates, namely Sapphire, AlN/Sapphire, Al0.5Ga0.5N/Sapphire and GaN/Sapphire, where interfacial strain for overgrown nanostructures changes from compressive to tensile respectively. GaN nanostructures grown by metalorganic chemical vapor deposition (MOCVD) using identical growth parameters exhibit pyramidal morphologies under low or no mismatch strain, while highly strained structures with compressive strain evolve into prismatic shapes when grown in the c-crystallographic direction. In addition, it is shown that interfacial strain also affects the growth rate and alloy composition of ternary AlGaN nanostructures produced under identical conditions on different templates/substrates. AlGaN nanostructures grown under compressive strain show higher vertical and lower lateral growth rates when compared to those under tensile strain. Scanning electron microscopy, transmission electron microscopy and cathodoluminescene were used to characterize growth rates, shape and composition of the nanostructures. Observed variation in morphologies, growth rates and compositions are explained in terms of the strain dependency of adatom diffusion barriers on strained surfaces and Ehrlich-Schwoebel barriers across different crystallographic planes. Density functional (DFT) calculations were performed to determine the dependency of adatom diffusion on strained GaN and AlN surfaces.
Photoelectron- and Thermionic- Emission Microscopy of Barium/Scandium Thin Films on Tungsten
Authors: Vaughn Joel M. , Kordesch Martin 
Published: April 2011

AbstractCommercial scandium oxide doped thermionic cathodes have demonstrated current densities over 100 A/cm2. In order to understand the effect of Sc- and Ba- oxides on the emissivity of these cathodes we have imaged thin films of scandium oxide and barium oxide on tungsten foils using photoelectron emission microscopy and thermionic emission microscopy. Arrays of 100 um × 100 um squares of scandium and 25 um × 25 um squares of barium, 200 nm thick, were sputter deposited onto 50 um thick sheets of tungsten foil. Imaging squares of different sizes gives an unequivocal identification of each material and a completely consistent comparison of each material and cathode structure under identical conditions in one image.The metal squares oxidize in air before imaging. Each sample was heated in situ in a Bauer-Telieps style LEEM/PEEM used primarily in the ThEEM mode. The barium oxide squares emit below 875 K, and diffuse over the scandium below 875 K. Thermionic emission from scandium oxide squares is observed at temperatures significantly larger than 875 K. Failure of the barium oxide film cathode is through barium desorption. AES spectra show that the Sc does not desorb.While the origin of reduced emission temperature is commonly believed to be a result of a low work function monolayer of Ba and Sc oxides, in our study, the benefits of a combined Ba/Sc cathode are present in a thick (multi-layer), layered structure of barium oxide on top of a thick scandium oxide layer.
Mirror Electron Microscopy for Inspection of Flat Surfaces
Authors: Hasegawa Masaki , Shimakura Tomokazu 
Published: April 2011

AbstractWe have developed a mirror electron microscope (MEM) for inspecting fine processed flat surfaces. This apparatus can detect nanometer-sized particles and scratches on very flat surfaces. Its sensitivity for electric charge distribution is useful for detecting failures in microdevice patterns. In observation of an insulator surface with the MEM, complex features caused by small amount of charge distribution were observed in the images. We believe that the MEM can provide different methods for characterization of electrical behavior on insulator surfaces.
Exploration of the Ultimate Patterning Potential Achievable with Focused Ion Beams
Authors: Gierak Jacques , Bourhis Eric , Mailly Dominique , Patriarche Gilles , Madouri Ali , Jede Ralf , Bauerdick Sven , bruchhaus lars , Hawkes Peter , Biance Anne-Laure , Schiedt Birgitta , Auvray Loïc , Bardotti Laurent , Prevel Brigitte , Mélinon Pascal , Perez Alain , Ferré Jacques , Jamet Jean Pierre , Mougin Alexandra , Chappert Claude , Mathet Véronique , Aigouy Lionel , Robert-Philip Isabelle , Sagnes Isabelle , Braive Rémy , Beveratos Alexios , Abram Izo 
Published: April 2011

AbstractDecisive advances in the fields of nanosciences and nanotechnologies are intimately related to the development of new instruments and of related writing schemes and methodologies. Therefore we have recently proposed exploitation of the nano-structuring potential of a highly Focused Ion Beam as a tool, to overcome intrinsic limitations of current nano-fabrication techniques and to allow innovative patterning schemes urgently needed in many nanoscience challenges. In this work, we will first detail a very high resolution FIB instrument we have developed specifically to meet these nano-fabrication requirements. Then we will introduce and illustrate some advanced FIB processing schemes. These patterning schemes are (i) Ultra thin membranes as an ideal template for FIB nanoprocessing. (ii) Local defect injection for magnetic thin film direct patterning. (iii) Functionalization of graphite substrates to prepare 2D-organized arrays of clusters. (iv) FIB engineering of the optical properties of microcavities.
Comparing the Role of Dislocations during Plastic Deformation of Nanocrystalline Nickel and Coarse-Grained Nickel during Cold Rolling
Authors: Kulovits Andreas , Mao Scott M , Wiezorek Jorg M 
Published: April 2011

AbstractWe investigated plastic deformation of fully dense electrodeposited nanocrystalline (NC) Ni with an average grain size of 30-40nm. We studied the microstructural evolution during cold rolling of NC Ni to a reduction in thickness up to 76% (true strain equivalent ∼1.42). We determined changes in texture, grain morphology, grain boundary character and grain sizes as a function of cold rolling strain, using X-ray diffraction and transmission electron microscopy TEM. We compared our results of the NC Ni with our own results for cold rolled coarse grained (CG) Ni. Differences and similarities in deformation behavior are discussed with respect to well documented findings in the literature.
Numerical Simulation of Twin-Twin Interaction in Magnetic Shape-Memory Alloys
Authors: Chmielus Markus , Carpenter David , Geleynse Alan , Hagler Michael , Schneider Rainer , Müllner Peter 
Published: April 2011

AbstractTwin boundary motion is the mechanism that drives the plastic deformation in magnetic shape memory alloys (MSMAs), and is largely dependent on the twin microstructure of the MSMA. The twin microstructure is established during the martensitic transformation, and can be influenced through thermo-magneto-mechanical training. For self-accommodated and ineffectively trained martensite, twin thickness and magnetic-field-induced strain (MFIS) are very small. For effectively trained crystals, a single crystallographic domain may comprise the entire sample and MFIS reaches the theoretical limit. In this paper, a numerical simulation is presented describing the twin microstructures and twin boundary motion of self-accommodated martensite using disclinations and disconnections (twinning dislocations). Disclinations are line defects such as dislocations, however with a rotational displacement field. A quadrupole solution was chosen to approximate the defect structure where two quadrupoles represent an elementary twin double layer unit. In the simulation, the twin boundary was inclined to the twinning plane which required the introduction of twinning disconnections, which are line defects with a stress field similar to dislocations. The shear stress - shear strain properties of self-accommodated martensite were analyzed numerically for different initial configurations of the twin boundary (i.e. for different initial positions of the disconnections). The shear stress - shear strain curve was found to be sensitive to the initial configuration of disconnections. If the disconnections are very close to boundaries of hierarchically higher twins – such as is the case for self-accommodated martensite, there is a threshold stress for twin-boundary motion. If the disconnections are spread out along the twin boundary, twinning occurs at much lower stress.
Very Low-Temperature, Gram-Scale Synthesis of Monodisperse BaTiO3 Nanocrystals via an Interfacial Hydrolysis Reaction
Authors: Morse Daniel E. , Brutchey Richard L. 
Published: April 2011

AbstractA vapor diffusion sol-gel method is reviewed for the preparation of high-quality BaTiO3 nanocrystals on the gram scale at very low temperatures. The synthesis is based on the kinetically controlled introduction of water into a solution of the bimetallic alkoxide, BaTi(O2C4H9)6, where slow hydrolysis then occurs at the vapor-solution interface followed by nucleation and nanocrystal growth at 16 °C. The resulting 6-nm, quasi-spherical nanocrystals are both monodisperse (without stabilizing agents or size selecting purification) and highly crystalline (without any post-synthesis heat treatment), and are isolated in yields near 100%. Based on new permittivity and calorimetry data, the crystal structure of the nanocrystals is most likely in the paraelectric cubic phase (space group Pm3m) at room temperature, which corroborates previous diffraction data. It was also demonstrated that the BaTiO3 nanocrystals can be doped with trivalent lanthanum cations using the same low-temperature vapor diffusion sol-gel method to yield donor-doped Ba1−xLaxTiO3, which exhibits a considerable PTCR effect.
Fabrication of Hollow Anatase Structure by Using Sea Wool Sponges
Authors: Kwong Fung-luen , Ng Dickon H. L. 
Published: April 2011

AbstractHighly porous carbon-doped anatase was produced by a simple and time-saving method. The product was prepared by using sea wool sponges and a titanium-contained organic solution. The intermediate product was pyrolyzed sponges coated with amorphous anatase. When further annealed, the final product was an entirely carbon – anatase product with the original structure of sea wool sponges. The struts in the carbon – anatase product were hollow with wall thickness less than 300 nm. Cathodoluminescence measurement showed that this C-TiO2 product was sensitive to visible light.
Synthesis of Biomorphic Silicon Carbide from Wood
Authors: Li Kwok Cheung , Ng Dickon H. L. 
Published: April 2011

AbstractWe have successfully produced biomorphic SiC ceramics from silica-infiltrated wood samples of balsa (Ochroma pyramidale) and flame tree (Delonix regia). This conversion of wood sample to a structure of SiC was performed by a sol-gel technique and a carbothermal reduction process. The biomorphic products were confirmed containing β-SiC and their structures were replica of the original structures of the raw wood samples. The biomorphic products from the denser flame tree (C-SiC) had higher specific strength than that from the biomorphic product from balsa (SiC).
Bio-Inspired Nano-Composite Fabrication on Etched Human Enamel Surface
Authors: Fan Yuwei , Sun Zhi , Moradian-Oldak Janet 
Published: April 2011

AbstractBecause of its significant potential in controlling key steps of apatite mineralization, recombinant amelogenin has been applied in different in vitro systems for the synthesis of uniquely ordered composite material similar to enamel. Here we summarize the results of a series of experiments, in which mineral deposition took place on the exposed surface of enamel from extracted human third molars soaked in calcium phosphate solution, in the presence of amelogenin and fluoride. Analysis of crystal size and morphology revealed that in the presence of both amelogenin (50-100 μg/mL) and fluoride (1 ppm), bundles of oriented rod- like fluoridated apatite crystals were formed creating a dense coating on the enamel substrate. Such organized bundles were not formed at low concentrations of rP172 (< 30 μg/mL). Preparation of such ordered nanocomposites provides a promising approach for development of new generation of dental restorative materials with improved esthetic and mechanical properties.
Measurement of Forces Generated by Chemomechanical Protein Aggregates Using Polymer BioMEMS
Authors: Ferrell Nicholas , Schwan Stefan , Spohn Uwe , Heilmann Andreas , Hansford Derek 
Published: April 2011

AbstractP-protein bodies (forisomes), in phloem cells of legumes, transform the chemical free energy of their reaction with alkaline earth metal ions into mechanical energy. In addition to using the bending of glass fibers, micromechanical forces generated by the switching of forisomes in aqueous solutions were measured by monitoring the bending of microscale polymer cantilever beams. The forisomes were fixed by chemisorption to the tips of four orthogonal beams of a BioMEMS microsystem designed and manufactured using the process of sacrificial layer micromolding. The sensor layout allows force measurements in the longitudinal and radial direction of the forisomes. For different forisomes a longitudinal force in the range from 84-136 nN and a radial force of 22-61 nN were measured.
Electrically Switchable Liquid Crystal Polymer Rod Actuators
Authors: Shafran Matthew , Sierros Konstantinos , Huebsch Wade , Cairns Darran 
Published: April 2011

AbstractStimulus responsive liquid crystal nanorods, 60 μm in length and 200 nm in diameter, were fabricated by a template synthesis technique. The liquid crystal, RM 257, is a reactive monomer which polymerizes with the application of UV light. After polymerization the liquid crystal's orientational order is permanently “frozen”. Therefore, the subsequent structures are temperature independent after curing. In this study the liquid crystal was confined in the pores of Anopore membranes before curing, which results in rod structures after photo-polymerization. After fabrication, the rods were observed under the application of both AC and DC electric fields. DC fields were noted by either up and down or translational movement of the rods. Application of AC fields resulted in random movement of the rods.
Nanoindentation of Histological Specimens using an Extension of the Oliver and Pharr Method
Authors: Akhtar Riaz , Sherratt Michael J , Bierwisch Nick , Derby Brian , Mummery Paul M , Watson Rachel E.B , Schwarzer Norbert 
Published: April 2011

AbstractThe micro-mechanical properties of 5 &#956;m thick histological sections of ferret aorta and vena cava were mapped as a function of distance from the outer adventitial layer using nanoindentation. In order to decouple the effect of the glass substrate on the elastic modulus of these thin sections, the nanoindentation data were analyzed using the extended Oliver and Pharr method which is readily accessible for coatings and layered materials with the software package, FilmDoctor®. In the aorta, the elastic modulus was found to decrease progressively from 35 MPa at the adventitia (outermost layer) to 8 MPa at the intima (innermost layer). This decrease in modulus was inversely correlated with elastic fibre density. In contrast, in the vena cava, the stiffest regions were found to be the adventitial (outer) and intimal (innermost) sections of the vessel cross-section. Both these regions were enriched in ECM components. The central region, thought to be largely cellular, had a relatively constant modulus of around 20 MPa. This study demonstrates that with this methodology it is possible to distinguish micro-mechanically between large arteries and veins, and therefore the same approach should allow age or disease related changes in the mechanical properties within a tissue to be quantified.
Design of a Dielectrophoretic Mechanical Testing Device
Authors: Manomohan Greeshma , Rajendran Kavitha , Morss Clyne Alisa 
Published: April 2011

AbstractMechanics play a critical role in cell function in health and disease. While a variety of techniques exist to measure cell mechanics, no single device or testing method can answer all biomechanics questions. We have designed a novel dielectrophoretic cell mechanics device to apply piconewton forces to single, asymmetric attached cells without physical contact. This device uses negative dielectrophoresis to trap individual cells, after which cells attach to the device substrate. Negative dielectrophoresis is then used to apply compressive force to attached cells, and cell displacement is measured via microscopy.COMSOL software was used to model the two-dimensional electric and force fields. Based on modeling results, a quadrupole electrode configuration was designed in AutoCad,fabricated using microfabrication techniques, and tested with endothelial cells. A modeled quadrupole electrode with a 50 μm center diameter operating at 1 volt and 1 MHz generated 100's piconewtons of compressive force. This force was sufficient to trap both polystyrene beads and cells. While trapped cells did attach to the glass substrate, further refinement of the device is needed to maintain the cells in a healthy state.This dielectrophoretic mechanics testing device expands the existing biomechanics toolbox by providing a non-contact method to test mechanics of attached cells under diverse conditions. Future dielectrophoretic systems could allow tensile as well compressive forces, and when coupled with microfluidic systems, could test cell mechanics under fluid flow or a chemotactic gradient. This device will improve our understanding of cell mechanics in healthy cell function and how perturbation of the mechanical environment contributes to disease.