Glassy layers

In the modified chemical vapor deposition (MCVD) technique, the reactants are deposited on the inside of a rotating siUca tube. The hoUow tube is heated from the outside by a moving oxyhydrogen torch. The oxide soot condenses onto the tube walls ahead of the burner, and the soot is then sintered into a glassy layer as the burner passes over it. When deposition is complete, the tube and its contents are collapsed to form a soHd preform rod. 

Manganese-rich deposits usually take one of three forms A loosely adherent, friable, brown, or black deposit may occur (Fig. 4.5). A thin, dark, brittle, glassy manganese layer sometimes forms on heat transfer surfaces (Fig. 4.6). Nodular manganese deposits also occur (Fig. 4.7). Both nodular and glassy layers tend to occur on copper alloys. 

Figure 4.6 A thin, glassy layer of predominantly manganese oxide on the internal surface of a brass condenser tube. The many white spots are pits at fractures in the manganese layer.

It can be readily understood that the structure of the oxide, from which the reduced catalyst is prepared, plays an important role for the properties of the catalyst. This dependence has been proved experimentally by the influence which the rate of cooling of the oxides of a given catalyst composition shows upon the catalytic properties of the reduced catalyst. This effect can be interpreted by considering that in the reduced catalyst the promoters are distributed all over the surface and that it is, of course, highly important how they are distributed. This distribution cannot be independent of the way in which the promoters are present in the oxidic state, whether in solid solution in the magnetite, as separate crystals or as amorphous glassy layers. 

Low melting point phases (glassy layer) may form only over high Si02 areas of the particle surface. Pores in Al203 rich areas (Al-sol binder and alumina matrix) remain open. 

Equation (70) is a scaling invariant relation for the concentration-dependency of the elastic modulus of highly filled rubbers, i.e., the relation is independent of filler particle size. The invariant relation results from the special invariant form of the space-filling condition at Eq. (67) together with the scaling invariance of Eqs. (68) and (69), where the particle size d enters as a normalization factor for the cluster size only. This scaling invariance disappears if the action of the immobilized rubber layer is considered. The effect of a hard, glassy layer of immobilized polymer on the elastic modulus of CCA-clusters can be de-... 

Figure 5.33 shows the surface (a) and the cross section (b) of a typical HVSF-sprayed hydroxyapatite coating with a highly dense structure that attest to complete melting of the powder particles and superior adhering to the substrate. The dense coating resembles a glassy layer with non-identifiable lamella boundaries (see also Bolelli et al., 2014). 

As the temperature rises, the viscosity of the glass falls, and viscous flow of the glassy layer from between the grains can result in creep. The available models predict that the effective viscosity of the material is inversely proportional to the cube of the volume fraction /of the boundary phase, i.e.. 

A smooth flat surface layer free from cracks was generally discernible above the waffling. When the coating was scraped after ashing and viewed edge on, a 0.1 micron thick glassy layer was seen (Fig 5). It is anticipated that the unreacted sublayer of the... 

The drug released from the anterior surface of the CL is wasted due to absorption into the conjunctiva. There is, however, a possibility that the drying of the anterior surface leads to the formation of a thin glassy layer that could minimize the drug loss from the anterior surface. In any case, the drug released across the posterior surface will constitute at least 50% of the total amount released because the release conditions are likely perfect sink toward both the anterior and the posterior surfaces. Perfect sink conditions imply that the time scale for the drug molecules to be absorbed by the cornea or the conjunctiva is much shorter than the time scale for diffusion across the CL, and thus the drug concentrations in both the pre- and post-lens tear flhn are very small. ... 

Silicon oxide glassy layers have also been recently identified on groimd silicon surfaces [67] using energy dispersive spectroscopy. 

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