Plastic deformation of materials occurs by the motion of defects known as dislocations and disclinations. High-resolution transmission electron microscopy was used to directly reveal the individual dislocations that constitute partial disclination dipoles in nanocrystalline, body-centered cubic iron that had undergone severe plastic deformation by mechanical milling. The mechanisms by which the...

The nanocrystallization processes in Fe-Si-B-Nb-Cu and Fe-Nd-B(-Cu-Nb) amorphous alloys have been studied by transmission electron microscopy (TEM) and a three dimensional atom probe (3DAP). Cu additions are effective in refining the nanocrystalline microstructures of an Fe74.5Si13.5B8Nb3Cu1 alloy and an Fe3B/Nd2Fe14B nanocomposite microstructure. This is because Cu atoms form a high density of...

Total x-ray diffraction and atomic pair distribution function analysis have been used to determine the atomic ordering in nanocrystalline (∼1.5 nm in size) CeO2–ZrO2 prepared by a sol–gel route. Experimental data show that the oxides are a structurally and chemically inhomogeneous mixture of nanoscale domains with cubic-type and monoclinic-type atomic ordering, predominantly occupied by Ce and ...

Enhanced atomic migration was an early observation from experimental studies into nanocrystalline solids. This contribution presents an overview of the available diffusion data for simple metals and ionic materials in nanocrystalline form. It will be shown that enhanced diffusion can be interpreted in terms of atomic transport along the interfaces, which are comparable to grain boundaries in co...

We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15 nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-...

Bulk computational thermodynamics are extended to model binary poly/nanocrystalline alloys by incorporating grain boundary energies computed by a multilayer adsorption model. A new kind of stability diagram for equilibrium-grain-size poly/nanocrystalline alloys is developed. Computed results for Zr-doped Fe are validated by prior experiments and provide new physical insights regarding stabiliza...

Hydrogenated nanocrystalline silicon obtained by Hot-Wire Chemical Vapour Deposition has been incorporated as the active layer in bottom-gate thin-film transistors. These devices were electrically characterised by measuring in vacuum the output and transfer characteristics for different temperatures. The field-effect mobility showed a thermally activated behaviour which could be attributed to p...

Due to their limited length of structural coherence nanocrystalline materials show very diffuse powder X-ray diffraction patterns that are difficult to interpret unambiguously. We demonstrate that a combination of high-energy X-ray powder diffraction and atomic pair distribution function analysis can be used to both assess the geometry (i.e., size and shape) and determine the internal atomic or...

This review seeks to summarize the recent developments in the synthesis, structural characterization, properties, and applications in the ®elds of amorphous, bulk amorphous, and nanocrystalline soft magnetic materials. Conventional physical metallurgical approaches to improving soft ferromagnetic properties have relied on the optimization of chemical and microstructural features. Within the las...

A theoretical model for describing effective thermal conductivity (ETC) of nanocrystalline materials has been proposed, so that the ETC can be easily obtained from its grain size, single crystal thermal conductivity, single crystal phonon mean free path (PMFP), and the Kaptiza thermal resistance. In addition, the relative importance between grain boundaries (GBs) and size effects on the ETC of ...