Materials Literature
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Nanoindentation study of a single poly(L-lactic acid) nanofiber produced by the phase separation method was performed using an atomic force microscope (AFM) cantilever tip. Issues concerning the use of AFM for nanoindentation of polymer nanofibers were discussed. The Hertz theory of contact mechanics was used to analy…
A method for simultaneously thermostatting an atomistic region and absorbing energetic pulses impinging on the atormstic/continuum interface from the atomistic region is developed to operate within the framework of the coupled atomistic/discrete dislocation method. The approach inserts an additional Langevin damping t…
Flower-shaped ZnO nanostructures were grown on Si(100) and Si(111) substrates by cyclic feeding chemical vapour deposition without the use of a metal catalyst. The structures obtained on the Si(100) substrate exhibited triangle-shaped leaves with lengths and diameters in the ranges 300-400 and 90-130 nm, respectively.…
Fiber surface-enhanced Raman scattering (SERS) sensors show great potential for in vivo and in vitro detection. However, current probes based on end-polished fibers suffer from small signal due to their small active region. To overcome this, we propose and demonstrate a D-shaped fiber configuration to increase the det…
We report on the fracture behavior of nanoporous (np)-Au with an open sponge-like morphology of interconnecting ligaments on the nanometer length scale. Despite its macroscopic brittleness, np-Au is microscopically a very ductile material as ligaments strained by as much as 200% can be observed in the vicinity of crac…
Possibilities to realize a negative refraction in chiral composites in in dual-phase mixtures of chiral and dipole particles is studied. It is shown that because of strong resonant interaction between chiral particles (helixes) and dipoles, there is a stop band in the frequency area where the backward-wave regime is e…
The field sweep rate (v=dH/dt) and temperature (T) dependence of the magnetization reversal of a single-chain magnet (SCM) is studied at low temperatures. As expected for a thermally activated process, the nucleation field (H_n) increases with decreasing T and increasing v. The set of H_n(T,v) data is analyzed with a…
We demonstrate that semiconductor nanowires measuring just a few nanometers in diameter can be translated, rotated, cut, fused and organized into nontrivial structures using holographic optical traps. The holographic approach to nano-assembly allows for simultaneous independent manipulation of multiple nanowires, incl…
We study the effect of a central mass concentration (CMC) on the secular evolution of a barred disc galaxy. Unlike previous studies, we use fully self-consistent 3D N-body simulations with live haloes, which are known to be important for bar evolution. The CMC is introduced gradually, to avoid transients. In all cases…
The interaction between an edge dislocation and a void in copper is investigated by means of a molecular dynamics simulation. The depinning stresses of the leading partial and of the trailing partial show qualitatively different behaviors. The depinning stress of the trailing partial increases logarithmically with the…
The results of DC magnetization measurements under hydrostatic (helium-gas) pressure are reported for an ambient pressure superconductor Na0.35CoO2.1.4D2O and its precursor compound, the gamma-phase Na0.75CoO2 that is known to combine a metallic conductivity with an unusual magnetic state below ~22K. The obtained data…
A review is presented of molecular and mesoscopic computer simulations of liquid crystalline systems. Molecular simulation approaches applied to such systems are described, and the key findings for bulk phase behaviour are reported. Following this, recently developed lattice Boltzmann approaches to the mesoscale model…
<div class="htmlview paragraph">The intention of the presented work was to develop a new simulation tool that fits into a CFD (computational fluid dynamics) workflow and provides information about the soot particle size distribution. Additionally it was necessary to improve and use state-of-the-art measurement t…
The thermally activated annihilation of screw dislocation dipoles provides a rationale for the endurance limit in fatigue and for the onset of stage III hardening in single crystal monotonic stress–strain curves. Such annihilation amounts to the thermal diffusion of shear, which along with the diffusion of matter (edg…
The role of damage on the mechanical response of a heterogeneous material was investigated through X-ray tomography combined with in situ tensile deformation. This technique enables one to follow the same population of damage-nucleating particles throughout a tensile test. The results indicate that heterogeneity in th…
Small scale yielding around a mode I crack is analysed using polycrystalline discrete dislocation plasticity. Plane strain analyses are carried out with the dislocations all of edge character and modelled as line singularities in a linear elastic material. The lattice resistance to dislocation motion, nucleation, inte…
The analysis of the physical mechanisms controlling plastic flow in pure polycrystals satisfying to Von Mises conditions, whose grain size d is larger than about one micron (standard polycrystals), is shown to stem from the enhanced multiplication of dislocations induced by the locking of dislocations at grain boundar…
A two-dimensional version of the shear-transformation-zone (STZ) theory by Falk and Langer is explored numerically. Two different geometries are used to simulate uniaxial tension experiments where materials are subjected to constant strain rates. In the first setup, a rectangular specimen is given an imperceptible ind…
The wavelength-dependent second-harmonic generation (SHG) efficiency of two simple dipolar chromophores, 4-NO2C6H4N(H)Bun (1) and 4-NO2C6H4SN(H)But (2), was compared in solution and in the solid state. Hyper-Rayleigh scattering measurements at 532 nm provided comparable molecular first hyperpolarizabilities. Both comp…
Reflection measurements in the 25-35 nm region were made for Mg/SiC and Mg/Y2O3 multilayers kept in a low-humidity atmosphere for 4 or 5 years. Aged Mg/SiC multilayers keep their reflectances, and the reflectance value at 31.2 nm is 0.44 at 10 degrees of the normal angle of incidence. Aged Mg/Y2O3 multilayers change r…