Point defects in NiAl and other structural intermetallics have been studied using perturbed angular correlation of gamma rays (PAC), by which signals are detected from antisite atoms and/or lattice vacancies in the first few atomic shells of probe atoms. For samples of quenched NiAl having 50 to 54 at.% Ni, site-fractions of Ni-vacancies (proportional to the vacancy concentration) were found to...

Owing to their remarkable mechanical properties, carbon nanotubes have been employed in many diverse areas of applications. However, similar to any of the many man-made materials used today, carbon nanotubes (CNTs) are also susceptible to various kinds of defects. Understanding the effect of defects on the mechanical properties and behavior of CNTs is essential in the design of nanotube-based d...

A kinetic rate theory model, which includes the formation of cascade-induced clusters (CIIC), is presented. Comparison of the model to ion irradiation data on vanadium reveals the e€ects of helium generation and cascade-induced interstitial and vacancy clusters on microstructure evolution. The model is based on a simpli®cation of hierarchical rate equations for the clustering of helium bubbles,...

The annealing kinetics of mobile intrinsic defects in cubic SiC is investigated by an ab initio method based on density-functional theory. The interstitial-vacancy recombination, the diffusion of vacancies, and interstitials to defect sinks ~e.g., surfaces or dislocations! as well as the formation of interstitial clusters are considered. The calculated migration and reaction barriers suggest a ...

A ll solids at finite temperatures contain point defects such as vacancies and interstitials. Even at very low concentrations, such defects have a pronounced effect on the transport properties (e.g., electronic) of otherwise pure crystals. However, the effect of point defects on the thermodynamic properties of crystals is small, simply because the mole-fraction of defects is low—at least, in on...

The plastic deformation of bee 3He crystals has been studied near the melting curve, in the temperature range 0.65 K :::; T:::; 1.17 K, and for strain rates, E, from 2X 10to 2X 10sec-I. The resulting relations between strain rate and stress, at a given temperature, are accounted for in terms of dislocation climb and vacancy diffusion in the solid He. The temperature dependence of the strain rat...

Using first principles calculations for O vacancy diffusion on CeO(2)(111), we locate a surface diffusion mechanism, the two-step O vacancy exchange one, which is more favored than the most common hopping mechanism. By analyzing the results, we identify quantitatively the physical origin of why the two-step exchange mechanism is preferred.

In this article, the influence of various vacancy defects on the Young’s modulus of carbon nanotube (CNT) - reinforcement polymer composite in the axial direction is investigated via a structural model in ANSYS software. Their high strength can be affected by the presence of defects in the nanotubes used as reinforcements in practical nanocomposites. Molecular structural mechanics (MSM)/finite ...