Grain boundary networks should play a dominant role in determining the mechanical properties of nanocrystalline metals. However, these networks are difficult to characterize and their response to deformation is incompletely understood. In this work, we study the grain boundary network of nanocrystalline Ni and explore whether it can be modified by plastic deformation. Mechanical cycling at room...

The emergence of third-generation photovoltaics based on Si relies on tunable bandgap materials with embedded nanocrystalline Si. One of the most promising approaches is based on the mixed-phase Si1 - xCx. We have investigated the light absorption controllability of nanocrystalline Si-embedded Si1 - xCx produced by thermal annealing of the Si-rich Si1 - xCx and composition-modulated superlattic...

Deformation twins are often observed to meet each other to form multi-fold twins in nanostructured face-centered cubic (fcc) metals. Here we propose two types of mechanism for the nucleation and growth of four different single and multiple twins. These mechanisms provide continuous generation of twinning partials for the growth of the twins after nucleation. A relatively high stress or high str...

We report annealing studies of thin films of GaN and GaN:O prepared by ion assisted deposition. As-prepared films of stoichiometric tetrahedrally bonded GaN form nanocrystalline networks, but amorphous networks result with the inclusion of more than 10 at.% of oxygen. The annealed nc-GaN films show an increased average crystallite size, though even after a 700 C anneal the crystals are no large...

A powder form of Fe-based nanocrystalline Fe73Cu1Nb1.5V2 Si13.5B9 has been prepared and its longitudinally driven magneto-impedance (LDMI) effect has been studied as a function of the structural and magnetic changes induced by suitable thermal treatments for the first time. The experimental results show that the LDMI ratio increases as the annealing temperature increases in the range of 480–600...

Scanning probe microscopy techniques (SPM) have been applied to a rapidly improvement in the characterization of metal oxide nanocrystalline. These materials are widely used in photon-to-electricity conversion devices, such as dye-sensitized solar cells. The surface properties of such nanocrystalline determine the devices’ performance. SPM imaging of nanocrystal surfaces and nanoscale systems h...

Nanocrystalline magnesium ferrite is synthesized by high-energy ball milling. The formation of nanocrystalline ferrite phase is observed after 3 h of milling and its content increases with milling time. The structural and microstructural evolution of the nanophase have been studied by X-ray powder diffraction and the Rietveld method. After 3 h of milling, ferrite phase (mixed spinel) nucleates ...

In the microcrystalline regime, the electrical (impedance/dielectric) behavior of grain boundarycontrolled electroceramics is well described by the “brick-layer model” (BLM). In the nanocrystalline regime, however, grain boundary layers can represent a significant volume fraction of the overall microstructure. Simple boundary-layer models no longer adequately describe the electrical properties ...

Amorphous and nanocrystalline carbon films possess special chemical and physical properties such as high chemical inertness, diamond-like properties, and favorable tribological proprieties. The materials usually consist of graphite and diamond microstructures and thus possess properties that lie between the two. Amorphous and nanocrystalline carbon films can exist in different kinds of matrices...

An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in convention...