Nucleation and propagation

Concrete is an inherently brittle material with low tensile strength and strain capacities. Its brittle characteristics lead to easy nucleation and propagation of cracks, thus restricting its range of applications. To address this deficiency, fibers of different materials such as asbestos, glass, metal, and synthetics " are used as additives, with the following results"" ... 

In the study of the nucleation and propagation of dislocations (Figure 10.11) from scratches in a geometry designed to produce slip on non-basal planes, edge dislocations were found to glide on non-basal planes, but screw dislocations were completely immobile except in the basal plane. Detailed measurements of the dislocation velocities using stress pulse techniques showed that... 

This is established by relating the usual nucleation and propagation parameters a and s of the Zimm-Bragg theory2 to the rate constants, Eq. (I), as follows ... 

M. Mundschau, M. E. Kordesch, B. Rausenberger, W. Engel, A. M. Bradshaw, and E. Zeitler, Real-time observation of the nucleation and propagation of reaction fronts on surfaces using photoemission electron microscopy. Surf. Sci., 227 (1990) 246. 

Physical transformations (usually solid-state crystallization) are more often directly linked to molecular mobility and orientation than the most common chemical reactions (oxidation and hydrolysis) thus the major stability concern for amorphous materials is with their tendency to revert to the crystalline state. As with all crystallization processes, there are the normal nucleation and propagation (crystal growth) stages to consider, and procedures that increase the barrier to nucleation or slow the rate of crystal growth can be used to physically stabilize many amorphous materials. 

In the other models, the hydrophobic methyl groups of the polypeptide backbone are envisioned to play more major roles. Generally, methyl groups can assume the role of either spacer molecules, barrier molecules, or hydrophobic matrices for heterogeneous nucleation and propagation. 

These quantities are often cast in the form of an equilibrium constant, with a and s representing the equilibrium constants for the nucleation and propagation steps, respectively (eq 8)... 

The mechanical interaction between the different epitaxial layers may result in the formation of misfit dislocations. Nucleation and propagation of cracks can ensue if the mismatch in thermal expansion coefficient is relatively large. The defects significantly influence the physical properties of the thin films. Examples from different material combinations and models of how to predict the numbers for critical thicknesses are provided in Section 14.4. 

There are a number of methods for the S5mthesis of different upon nature nanoparticles and nanomaterials, however the kinetic peculiarities and regularities of the formation (nucleation and propagation) of nanoparticles studied insufficiently. 

Delamination Wear Involves material removal subsequently to plastic deformation, crack nucleation, and propagation in the subsurface (Jahanmir and Suh, 1977 Suh, 1986)... 

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