Aluminum surface distribution

Figure 12-10. Cumulative distribution of peak heights for bead-blasted aluminum surface for which the profilometric trace is shown at the top. The peak heights are with respect to an arbitrary datum below the surface the distribution is with respect to an envelope representing the of the surface. Scale shows the surface roughness of the...

Figure 2 The surface distribution of (A) aluminum, (B) gallium, and (C) zirconium and hafnium from coastal to open ocean regions in the North Pacific and western North Atlantic. Note the scale changes between oceans. In all panels, the coastal locations are plotted at the outside edges, with more oceanic locations in towards the middle. The data for Al and Ga in the eastern North Pacific are from 28°N 155°W to 36°N 123°W (Orians and Bruland, 1986, 1988b). For the Atlantic, the Ga data are from 37°N 75°W to 36°N 73°W (Orians and Bruland, 1988b), and the Al data are from Rhode Island, across the Gulf Stream, into the Sargasso Sea, then down toward the Caribbean (Measures et al, 1984, stations 0-1206). For Zr and FIf the western North Pacific data are from 38°N 146°E to 16°N 169°W, and in the eastern North Pacific from 50°N 145°W to 49°N 126°W (McKelvey and Orians, 1993 McKelvey, 1994).

Spatial Distribution of Chromium on the Aluminum Surface Treated by Aqueous Chromium(III) Pumarato Solution... 

Figure 3.9 Normalized energy distributions of sputtered Aluminum atoms resulting from 17.5 KeV Ar and Cs impact on an Aluminum surface at an impact angle of 20 as defined by MARLOWE (symbols) overlaid that predicted by the Sigmund-Thompson relation as defined by Relation 3.4 (lines). Reprinted with permission from van der Heide and Karpusov (1998) Copyright 1998 John WUey and Sons.

Aluminum diffusion distributions also have complicated profiles consisting of an abrupt near-surface region and a less sharp volume region. Parameters of diffusion depend on surface concentration, and there is a slight increase of the diffusion coefficient with decreasing Al concentration from 5 X 10 to 10 cm ... 

As the amount of Ti—Zr oxide deposited during Ti—Zr-based pretreatment is affected by die type, fractional area and distribution of cathodic particles present on the aluminum surface, the pretreatment conditions should be adapted to the specific alloy to achieve optimum performance... 

The equivalent isotropic temperature factors, B, are remarkably similar, atom for atom, in the two stmctures, and the equality of the temperature factors for all four tetrahedral cations (0.65, 0.65, 0.62, 0.63) immediately suggests that the aluminum-silicon distribution is identical in all four positions. A careful consideration of the apparent anisotropic thermal motion of the surface oxygens strongly suggests that the arrangement of and Na ions within either stmcture is completely random there is no evidence for segregation either into different layers or to different domains within a layer. 

Traditional adsorbents such as sihca [7631 -86-9] Si02 activated alumina [1318-23-6] AI2O2 and activated carbon [7440-44-0], C, exhibit large surface areas and micropore volumes. The surface chemical properties of these adsorbents make them potentially useful for separations by molecular class. However, the micropore size distribution is fairly broad for these materials (45). This characteristic makes them unsuitable for use in separations in which steric hindrance can potentially be exploited (see Aluminum compounds, aluminum oxide (ALUMINA) Silicon compounds, synthetic inorganic silicates). 

Rosin sizing usually involves the addition of dilute aqueous solutions or dispersions of rosin soap size and alum to a pulp slurry (44—46). Although beater addition of either coreactant is permissable, addition of both before final pulp refining is unwise because subsequently exposed ceUulose surfaces may not be properly sized. The size and alum should be added sufficiendy eady to provide uniform distribution in the slurry, and adequate time for the formation and retention of aluminum resinates, commonly referred to as size precipitate. Free rosin emulsion sizes, however, do not react to a significant degree with alum in the pulp slurry, and addition of a cationic starch or resin is recommended to maximize retention of size to fiber. Subsequent reaction with aluminum occurs principally in the machine drier sections (47). 

Aluminum resinate particles, ie, size precipitate, are attracted to the fiber surfaces because of a difference in charge and thus are retained (45,46,54). In general, the particles of size precipitate are small and are distributed fairly uniformly over the sheet. However, on drying, there is some sintering of the particles which helps to redistribute them on the fibers. 

The large majority of activated alumina products are derived from activation of aluminum hydroxide, rehydrated alumina, or pseudoboehmite gel. Other commerical methods to produce specialty activated aluminas are roasting of aluminum chloride [7446-70-0], AIQ calcination of precursors such as ammonium alum [7784-25-0], AlH2NOgS2. Processing is tailored to optimize one or more of the product properties such as surface area, purity, pore size distribution, particle size, shape, or strength. 

Rehydration Bonded Alumina. Rehydration bonded aluminas are agglomerates of activated alumina, which derive their strength from the rehydration bonding mechanism. Because more processing steps are involved in the manufacture, they are generally more expensive than activated aluminum hydroxides. On the other hand, rehydration bonded aluminas can be produced in a wider range of particle shape, surface area, and pore size distribution. 

External Coils and Tracers Tanks, vessels, and pipe hnes can be equipped for heating or cooling purposes with external coils. These are generally 9.8 to 19 mm (% to V4 in) so as to provide good distribution over the surface and are often of soft copper or aluminum, which can be bent by hand to the contour of the tank or hne. When necessary to avoid hot spots, the tracer is so mounted that it does not touch the tank. 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Surface water enrichment is the result of aeolian and fluvial inputs, which are thought to be the most important sources of Th to the ocean. Thorinm-232 has been proposed as a link between the radiogenic thorium isotopes and trace metals and anthropogenic pollutants. " While the pathways are very different for the radiogenic thorium isotopes, Th is delivered to the ocean in a fashion similar to many pollutants and trace metals. For example, Guo et found Th distributions in the Gulf of Mexico and off Cape Hatteras in the North Atlantic Ocean agreed well with the general distribution pattern of aluminum. 

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