Surface scaling

Fig. XI-6. Polymer segment volume fraction profiles for N = 10, = 0-5, and Xi = 1, on a semilogarithinic plot against distance from the surface scaled on the polymer radius of gyration showing contributions from loops and tails. The inset shows the overall profile on a linear scale, from Ref. 65.

E. Eisenriegler, K. Kremer, K. Binder. Adsorption of polymer chains at surfaces Scaling and Monte Carlo analysis. J Chem Phys 77 6296-6320, 1982. 

Sodium hydroxide (NaOH) and potassium hydroxide (KOH) solutions do not dissolve tantalum, but tend to destroy the metal by formation of successive layers of surface scale. The rate of the destruction increases with concentration and temperature. Damage to tantalum equipment has been experienced unexpectedly when strong alkaline solutions are used during cleaning and maintenance. 

When cast iron is exposed to high temperatures under oxidising conditions, oxidation of the metal results, with the formation of a surface scale. In addition, the dimensions of the component become distorted. Although such dimensional changes can occur also in inert atmospheres or in vacuum, the evidence available suggests that this growth is frequently associated with oxidation, and accordingly it is appropriate to consider it as an aspect of the corrosion of the iron. 

Porosity Gas absorption Remove surface scale Remove surface moisture Cleaner gas shield... 

Advance warning should be had from the plant running log of any build-up of scale on water-cooled surfaces. Scale within the tubes of a straight double-pipe or shell-and-tube condenser can be mechanically removed with suitable wire brushes or high-pressure water lances, once the end covers have been removed. Tubes which cannot be dealt with in this way must be chemically cleaned (see also Chapter 33). 

Solar lentigo circumscribed pigmented macule, no surface scaling... 

Acid pickling. Steel products are immersed in heated acid solutions to remove surface scale during pickling operations. This generates wastewater from three sources ... 

Factors involved in heat transfer, such as surface-to-volume ratio, agitation characteristics, mixing efficiency, fouling of heat transfer surfaces, scale of operations, and the resulting heat exchanged depend on the system under consideration (e.g., liquid-liquid transfer, liquid-gas transfer, free convection, or forced convection). Standard chemical engineering texts and reference books contain detailed discussions on heat transfer in process equipment. Only a brief summary follows ... 

Air-water flow regimes, 22 773 Air-water interface, molecular recognition at, 26 799-800 AISI 403 alloys, 23 511 AISI alloy steels, 23 299-300 Ajmalicine, 2 94, 95, 96, 100 Ajmaline, 2 94, 95, 96-97 AK-UFVE contactor, 20 768 A1203 surface scale, 23 507-508 Alabaster, 4 583... 

Chromium compounds Cr203 surface scale Nickel- chromium—iron alloys Nickel-chromium— molybdenum (tungsten) alloys Ni-Cr alloys analytical methods, 6 502-514 composition of metal compared to chromium ferroalloys, 6 501t dispersoid former, 2 325, 327 disposal, 6 519-521 economic aspects, 6 496—500 effect on cobalt alloys, 7 220 effect on stainless steel corrosion resistance, 7 809... 

CP Matrix Pinch system, 13 199, 206 CpTi-R bond, 25 119-120. See also Cyclopentadiene Cr2C>3 surface scale, 13 511 CR-39 casting resin, 19 798-799 Crabbing, 9 183 Crabs... 

The EDX spectrum (Fig. 11.8) shows the main surface scale impurity peaks of silica, aluminium, sodium, chloride and iron. If this EDX is compared to that of a new, clean membrane surface (Fig. 11.9), the clean surface shows sulphur, carbon and oxygen, which is typical of a porous polysulphone support. It was concluded that the scale is amorphous, composed of aluminosilicate and silicate. These compounds are normally found in trace amounts in brine solutions. Analysis showed that the surface could be cleaned with hydrochloric acid and analysis of the dissolved scale was similar to the EDX spectrum analysis. Review of the plant operation determined that the precipitation was the result of high pH in combination with high silica concentrations in the brine. 

Regarding the electrochemical method, the generalized forms of the Cottrell relation and the Randles-Sevcik relation were theoretically derived from the analytical solutions to the generalized diffusion equation involving a fractional derivative operator under diffusion-controlled constraints and these are useful in to determining the surface fractal dimension. It is noted that ionic diffusion towards self-affine fractal electrode should be described in terms of the apparent self-similar fractal dimension rather than the self-affine fractal dimension. This means the fractal dimension determined by using the diffusion-limited electrochemical method is the self-similar fractal dimension irrespective of the surface scaling property. 

The arguments behind the d band model are quite general and should apply to the interactions in the transition state as well as in the initial and final (adsorbed) states of the process. We therefore expect correlations between the d band center and transition state energies to be the same as for chemisorption energies. This is illustrated in the bottom panel of Figure 4.10. Figure 4.16 shows in detail how the activation energy for methane on different Ni surfaces scales with the center of the d bands projected onto the appropriate metal states to which the transition state couples. 

Long-term exposure of composites to oxidative environments can have deleterious effects on short-term mechanical behavior, such as resistance to crack initiation. This is particularly true in the case where the composite oxidizes to form an oxide surface scale. Although such reactions can be beneficial in limiting oxidation reactions, when the composite is subsequently cooled to room temperature, the reaction product can be a source of flaws and increase the composite s susceptibility to crack initiation. The following example illustrates this point. 

Figure 5. Geschmackeslupe for presenting flowing stimuli to oral surfaces. Scale = 1 cm. I - inflow port, 0 - outflow port, T - port for stimulation, approximately 1 cm in diameter. Inflow and outflow tubes in the barrel are concentric.

Fig. 4.9 SEM images to illustrate the nanostructures on gold-coated C. cells cicada wings taken (a) at an angle to the surface of the wing, and (b) from a direction normal to the upper surface. Scale bars are 1 pm and 2 pm in (a) and (b) respectively (Reproduced with permission from [28])...

As a result one gets the intensity of the backscattered particles as a function of their energy. By applying the formula for the energy loss of ions in matter one converts this into a depth below the surface scale for a homogeiieous target. If the target contains more than one element, the situation is more complicated because of... 

MULTISCALE DESCRIPTION OF COMPLEX SURFACES Scaling concepts... 

The surface property of a solid is characterized by the nature of the surface boundary. The surface boimdary is expected to be related to the underlying geometric nature of the surface, hence its fractal dimension. Many properties of the solid depend on the scaling behavior of the entire solid and of the pore space. The distribution of mass in the porous solid and the distribution of pore space may also reflect the fractal nature of the surface. If the mass and the surface scale are alike, that is, have the same power-law relationship between the radius of a particle and its mass, then the system is referred to as a mass fractal. In a similar manner if the pore volume of porous material has the same power-law relationship between the pore volume and radius as that of the surface, then it is described as a pore fractal. 

Fig. 23. The change in Si content of the surface as a function of the ion fluence. The thickest curve is the average of the three data sets. At steady state, the slope of this line is the etch yield of Si, 0.06 Si/ion. The dotted curve is data from the larger (1000- A ) surface, scaled by a factor of 0.5 in both dimensions, and is not included in the average. (From Abrams and Graves, 1999.)...

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