In recent years, near-nano (submicron) and nanostructured materials have attracted increasingly more attention from the materials community. Nanocrystalline materials are characterized by a microstructural length or grain size of up to about 100 nm. Materials having grain size of $0.1 to 0.3 mm are classified as submicron materials. Nanocrystalline materials exhibit various shapes or forms, and possess unique chemical, physical or mechanical properties. When the grain size is below a critical value ($10-20 nm), more than 50 vol.% of atoms is associated with grain boundaries or interfacial boundaries. In this respect, dislocation pile-ups cannot form, and the Hall-Petch relationship for conventional coarse-grained materials is no longer valid. Therefore, grain boundaries play a major role in the deformation of nanocrystalline materials. Nanocrystalline materials exhibit creep and super plasticity at lower temperatures than conventional micro-grained counterparts. Similarly, plastic deformation of nanocrystalline coatings is considered to be associated with grain boundary sliding assisted by grain boundary diffusion or rotation. In this review paper, current developments in fabrication, microstructure, physical and mechanical properties of nanocrystalline materials and coatings will be addressed. Particular attention is paid to the properties of transition metal nitride nanocrystalline films formed by ion beam assisted deposition process. #

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Magnetic-field-induced electric polarization in nanostructured multiferroic composite films was studied by using the Green's function approach. The calculations showed that large magnetic-field-induced polarization could be produced in multiferroic nanostructures due to enhanced elastic coupling interaction. Especially, the 1-3 type films with ferromagnetic nanopillars embedded in a ferroelectric matrix exhibited large magnetic-field-induced polarization responses, while the 2-2 type films with ferroelectric and ferromagnetic nanolaminates showed much weaker magnetoelectric coupling and lower magnetic induced polarization due to large in-plane constraint effect, which was in agreement with the recent observations.

Organic/inorganic nanocomposites (OINs) can be potentially used as high-performance capacitors due to their rapid charge-discharge capability along with respectable power density. The coupling effect of the filler/matrix interface plays a prominent role in the dielectric and electric properties of OINs. Along with a review of contemporary theoretical models, recent advances in interfacial optimization to improve energy density through careful interface control and design are also presented. Possible mechanisms that may improve energy density and potential applications for high-energy-density capacitors are also highlighted.

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A beam of monochromatic synchrotron x-ray incident on a silicon wafer creates a rich intensity pattern behind the wafer that reflects the cross section of scattering by thermally populated phonons. A least-squares fit of the patterns based on a lattice dynamics calculation yields the phonon dispersion relations over the entire reciprocal space. This simple and efficient method is suitable for phonon studies in essentially all materials, and complements the traditional neutron scattering technique. PACS numbers: 78.70.Ck, 63.20.Dj Phonons are the fundamental quanta of lattice vibration in a solid. They play a critical role in phenomena such as superconductivity and many types of phase transitions, and are the basis for the acoustic, thermal, elastic, and infrared properties of solids [1]. A fundamental description of phonons is the dispersion relation, which is determined traditionally through neutron scattering [2][3][4] or, more recently, through inelastic x-ray scattering [5]. However, these methods can be technically demanding, and alternative, complementary methods have been long sought. This study demonstrates a new approach based on x-ray intensity patterns produced by scattering from thermally populated phonons using silicon as a test case. Intensity patterns with a wide dynamic range were recorded in a matter of seconds at the third-generation synchrotron, the Advanced Photon Source. A least-squares analysis in terms of lattice dynamics yields dispersions for all six phonon branches in excellent agreement with neutron scattering results. The fast data acquisition rate, simplicity of the experiment, and a minimal requirement on sample volume make this method attractive for a wide range of applications in materials research.Although intensity distribution of x-ray scattering by thermally populated phonons has been long recognized as a possible measure of phonon properties [6][7][8], this method has remained impractical and attracted little interest. The situation has changed due to recent advances in synchrotron radiation instrumentation and computational power. Undulator beams at third-generation synchrotrons, such as the Advanced Photon Source, now yield a brightness about 8 orders of magnitude higher than a conventional laboratory source. In addition, the use of two-dimensional detectors such as the image plate used in this experiment allows parallel detection over a large scattering solid angle, effectively increasing the data collection rate by 6 orders of magnitude. The combined improvement makes it possible to carry out such measurements with a high degree of precision and efficiency. Intensity patterns recorded from both Si (111) and Si(100) in a transmission mode, displayed on a logarithmic scale, reveal details of intensity variation that are uniquely related to phonon modes over a wide range in the reciprocal space, thus enabling a determination of the phonon dispersions.Our experiment was performed at the undulator beam line of Sector 33 (University, Industry, and National Laboratory Collabor...

Real-time in situ x-ray studies of continuous Pb deposition on Si(111)-(7x7) at 180 K reveal an unusual growth behavior. A wetting layer forms first to cover the entire surface. Then islands of a fairly uniform height of about five monolayers form on top of the wetting layer and grow to fill the surface. The growth then switches to a layer-by-layer mode upon further deposition. This behavior of alternating layer and island growth can be attributed to spontaneous quantum phase separation based on a first-principles calculation of the system energy.

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