Surface-assisted phenomenon

Role of Ciystallographic Shear Planes This area is tied to the subject of surface oxidation state. In redox kinetics it is believed that sites for hydrocarbon oxidation are different from that for reoxidation, and crystallographic shear planes (CSP) have been suggested to assist bulk oxygen movement between the sites 44,45,46,47), There have been a few studies of this phenomenon. In WO2.95 WO2.9 it has been shown CSPs are involved in oxygen transfer but... 

The risk of devitrification rises the longer a glass is kept in a softened or melted state, and it is also linked to how dirty the glass is. Devitrification typically begins as a surface phenomenon, using either dirt or some other surface defect as a nucle-ation point. The devitrification process may be assisted by variations in the exte-... 

Characteristics of the solvent. Solvent properties affect US-assisted digestion as they impose the cavitation threshold above which sonochemical effects are felt by the medium. Also, any phenomenon altering some solvent property can modify such a threshold. Thus, any change in temperature results in a change in solvent properties such as the vapour pressure, viscosity or surface tension, which affect cavitation and their effects as a result. 

Another phenomenon that may affect the critical moisture content is known as case-hardening. In this instance, the surface of the material is dried so rapidly that a layer of dry, non-porous material forms. This over-dried surface acts as a barrier to moisture diffusion, since diffusivity decreases with moisture concentration. This may occur in vacuum drying, which will be discussed later in the chapter. To reduce the risk of case-hardening, the relative humidity of the drying gas may be increased to assist in maintaining a higher surface EMC until the internal moisture has diffused to the surface. 

As well, a notch may do the same with regard to the diffusion from the points of view of the geometry and the stress effects on the transport phenomenon, if compared with the stress-unassisted diffusion in a smooth cylinder. In particular, the range of the disturbing effect of a notch on stress in assisted transport phenomena in solids can be estimated from fig. 4, where vanishing of the notch effect corresponds to fairly radial flow trajectories, or concentration contour bands parallel to the cylinder surface, the same as it occurs in smooth bars. 

The conversion of benzyl chloride to benzyl cyanide proceeded further than the soluble silacrovm. There is insufficient data to determine whether this is a general phenomenon. It has been pointed out by other workers7 that silica provides an adsorptive surface that can provide assistance in phase transfer. The reaction of potassium cyanide with allyl bromide under liquid/liquid phase transfer conditions produced a mixture of allyl cyanide and crotononitrile. This may be compared to the cataysis exhibited by another new phase transfer catalyst, immobilized trimethoxysilyloctyltributylammonium bromide, which produced only allyl cyanide. 

The modulus at minimum and low strain amplitudes is due to the so-called filler network and it is accepted that the filler surface area, as well as the surface activity, play a major role in establishing a filler network, determining the effective contact area between filler particles and between filler particles and the elastomer matrix. The stress assisted disruption of the filler network causes the reduction of the modulus as the strain amplitude increases, giving rise to the non-linearity of the dynamic-mechanical behaviour of the rubber composite. This phenomenon is known as the Payne effect and it is (to a certain extent) reversible. The disruption and re-formation of the filler network is... 

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