Formation of holes

Pitting the formation of holes or pits in a metal surface, by corrosion. 

The dependence on film thickness is attributed to the dewetting nucleation, which occurs in the 2.5-4.5 nm thickness range via the formation of randomly distributed droplets rather than the formation of holes. When the initial film thickness exceeds 4.5 nm, dewetting is trigged via nucleation of holes instead of droplets, and for film thickness above 10 nm, dewetting develops slowly via hole nucleation at defects. The different dewetting processes observed for different initial film thicknesses can be explained in terms of the variation of disjoining pressure and the inability of the polymer to spread on its own monolayer. 

The values derived in this way for the diffusion coefficients exhibit surprising agreement with the experimental values, even for small ions, better than a coincidence in the order of magnitude. More detailed theoretical analysis indicates that the formation of holes required for particle jump is analogous to the formation of holes necessary for viscous flow of a liquid. Consequently, the activation energy for diffusion is similar to that for viscous flow. 

Foreign material contamination in a resin feedstock can destroy value to the processor by the production of off-specification product and by shutting down a line due to the formation of holes in a product web or a hole in a blown film bubble. To mitigate the economic loss, the processor must be able to identify the contaminant quickly so as to minimize the level of off-specification product. Moreover, the off-specification product needs to be isolated before a decision can be made to either... 

In full-scale applications very fast corrosion (formation of holes over the course of weeks, especially at improper welds) has been observed in off-gas piping, even when made from stainless steel. The problem is most evident when aerosols, for example containing chloride, escape from the reactor into the pipes where they form a very corrosive wet film. But corrosion may also occur in stainless steel pilot or full-scale reactors, especially when treating waste waters. Such reactors are best made of stainless steel because of the possibility to operate them at elevated pressures, e. g. 200-600 kPa, which can readily be achieved with commercially available ozone generators (Masschelein, 1994). 

Absorption of photons at 77K has the same initial effect as absorption at room temperature transfer of electrons to the conduction band and formation of holes in the valance band. 

It is remarkable that both quantities show very similar temperature dependences. It means that our microscopic EPR measurements and the macroscopic resistivity measurements by Ando et al. provide evidence of the same phenomenon the formation of hole-rich metallic stripes in lightly doped LSCO well below xcr = 0.06. This conclusion is also supported by a recent angle-resolved photoemission (ARPES) study of LSCO which clearly demonstrated that the metallic quasiparticles exist near the nodal direction below x=0.06 [16],... 

For a given strain rate, e, the temperature domain can be divided into two regions. At low temperatures, the fracture is brittle with a nearly constant stress, chain mobility and the fracture occurs from stress concentration at the defects, leading to the formation of holes and then crack propagation. 

X3A Corneal ulceration/keratomalacia Formation of holes on the cornea (involving less than a third of corneal surface)... 

Severe corrosion at the bottom of the phosphatizing tank was observed, which led to the failure of the tank through the formation of hole in the tank. Perforation was also observed in the tank, involving rinse cycle operation. During the operations the aluminum plates fall and reach the bottom of the tanks. Considerable corrosion was also observed in the portions of the tanks where the aluminum plates or filings are in close contact with the floor of the steel tank. 

Another approach to explain foam film rupture has been developed by de Vries [101] who proposed to consider film rupture as a result of fluctuational formation of holes (black spots) in it - nuclei of critical size (see Section 3.4). This idea was used in the analysis of the... 

Theoretical analysis of sheeting in the drainage of thin liquid films has been conducted in [359]. Sheeting dynamics and hole formation (i.e. black spot formation) was described by non-linear hydrodynamic stability analysis based on the equilibrium oscillatory structural component of disjoining pressure. The effect of stepwise thinning, accompanied by formation of holes , was described qualitatively. It is rather arguable whether the term holes for a black spot is appropriate since in 1980 holes in NBF were described as lack of molecules. The use the same term for two different formations is at least confusing. Besides, to have a hole in a CBF is almost as to have a hole in the sea water . 

The linear energy of the contact line between two-dimensional phases is only positive. Otherwise the mechanical equilibrium stability condition will be violated. This case is illustrated by examining the fluctuation formation of holes in bilayers. The linear energy of holes in between +6-10 12 J m 1 and +4.5-10 11 J m 1 (+6-10 7 dyn and +4.5-10 6 dyn). 

Knowing the values of (3 In D)/[3(l/7 )] both at constant pressure but also at constant volume, one can separate out the heats of activation the one for the formation of holes, and the one for jumping into holes. Some of the values obtained for ordinary liquids, molten metals, and molten salts are shown in Table 5.33. °... 

Thus, exposure of zeolites to high-energy radiation leads to the formation of holes and electrons, both of which react with water to produce OH and hydrated electrons. 

It can be concluded that the formation of the voids in the center of SnOi particles is mainly a result of the Kirkendall effect [8] associated with a faster outward diffusion of Sn atoms as compared to the inward diffiision of oxygen atoms in the process of the surface oxide layer formation. This produces high density of vacancies at the metal side of the metal/oxide interface. Vacancies transform to vacancy clusters which then aggregate into holes. It might be expected from this model that the increase of oxygen content in the ambiance will result in the promotion of an inward diffusion of oxygen atoms into the Sn particles, and therefore, suppress the formation of holes. 

To overcome this constraint, we performed experiments where we applied very short voltage pulses of only nanoseconds duration to an STM tip in electrochemical environment. The limited diffusion of the ions during such short voltage pulses prevented the ion distribution in the electrolyte from equilibration and indeed led to confinement of the electrochemical reactions on a nanometer scale. This method is demonstrated for the formation of holes of about 5-nm diameter and up to 3 monolayers (ML) depth on an Au(l 11) surface by local anodic dissolution of Au and for the local deposition of Cu clusters of similar dimensions by reduction of Cu ions from a CUSO4 electrolyte [16,17]. These experiments are reviewed and compared... 

Mechanisms describing the formation of holes of this type are based on the amplification of electrode surface coarseness52,53 in diffusion-controlled electrodeposition and to the tip54 and edge55 effects of current density distribution at electrode surface. More about these mechanisms can be found in Ref.13... 

This increase of the portion of channel structure to the overall structure of the deposit in relation to the portion of holes to the overall structure is probably due to changes of the properties of the electroplating solution, caused by the dependences of the viscosity and surface tension of solution on temperature. As a result of this, the formation of holes becomes less possible and hence large holes appear only due to the edge effect, as can be clearly seen from Fig. 40c. It is obvious that the probability of the formation of the nucleus of such a structure decreases with lowering of the break-off diameter of the bubbles. 

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