Subsurface composition

The cost of GSE Curtain Wall technology varies depending on site conditions. The cost of the HOPE ranges from 10 to 30/ft (D18980E, p. 17). According to the U.S. DOE, the cost of a synthetic barrier installation depends on the subsurface composition, depth, and method of installation. The DOE estimates that installation costs range from 20 to 250/m (D17096R, p. 2). 

Collisions can either result in net accretion, as demonstrated by the assembly of planets from planetesimals, or disruption, as in the case of the formation of the Moon. Even accretional collisions can redistribute materials far and wide, altering and perhaps blurring the distributions of compositionally distinct surface materials and exposing subsurface compositions. 

Fig. 7. Evolution of surface and subsurface composition of a sputtered PtNi alloy during annealing. Top schematic view bottom STM images of a Pt25Ni75(lll) sample (100x90 nm each) corresponding to these states. The misfit dislocations between the altered layer and the bulk are visible as a network of dark lines in the middle STM image (cf. Refs. 45,46).

OAquifer, subsurface (composite of sediments collected over 3-m span 12m below surface), and surface soil of Savannah River Site (SRS). Underlined pH values were measured from 1 2 (soihsolution) of 0.01 M CaCl2 solution. 

Even in the ab en(pe of preferential sputtering, i.e, SA=Sg, it is not necessarily the case that the concentration ratio of A and B is uniform with depth under steady state ion bombardment. The subsurface layer can have a different concentration ratio from the bulk or the top surface even if the latter two are identical. This can occur because of the subsurface effects of ion bombardment discussed below, which can produce an altered subsurface composition. As a result, there are two altered layers possible the top surface layer where composition at steady state is completely controlled by RgA and the subsurface layer where composition is controlled by segregation, radiation induced diffusion, radiation induced segregation, recoil implantation and cascade mixing. 

The subsurface composition change expected in a homogeneous binary alloy due to recoil implantation or knock-in is controlled by the maximum energy transfer possible and is characterized by the parameter... 

Ion beam sputtering is the primary process in SIMS, but as remarked earlier, it is also important in depth profihng, a method widely used in AES, XPS, SIMS, and many other techniques to study subsurface composition with quite fine depth resolution. When an ena-getic ion strikes a surface, it dissipates some of its energy into the surface. In the simplest case when the ion is scattCTed back out of the surface, the ena-gy transferred to a surface atom after a binary collision is sufficient to cause substantial local damage. Howeva-, when the incident ion is scattered into the solid, the result is a collision cascade leading to the emission of sputtered particles (ions, ionized clusters, atoms, and atomic clusters) from the... 

A number of other studies [23-29] of liquids and solutes in liquids have revealed similar differences between the surface and subsurface compositions. 

It is rare to be able to observe elastic deformations (which occur for instance during earthquakes) since by definition an elastic deformation does not leave any record. However, many subsurface or surface features are related to the other two modes of deformation. The composition of the material, confining pressure, rate of deformation and temperature determine which type of deformation will be initiated. 

As the conditions of pressure and temperature vary, the phases in which hydrocarbons exist, and the composition of the phases may change. It is necessary to understand the initial condition of fluids to be able to calculate surface volumes represented by subsurface hydrocarbons. It is also necessary to be able to predict phase changes as the temperature and pressure vary both in the reservoir and as the fluids pass through the surface facilities, so that the appropriate subsurface and surface development plans can be made. 

The previous equation is only valid as long as there is no compositional change of the gas between the subsurface and the surface. The value of E is typically in the order of 200, in other words the gas expands by a factor of around 200 from subsurface to surface conditions. The actual value of course depends upon both the gas composition and the reservoir temperature and pressure. Standard conditions of temperature and pressure are commonly defined as 60°F (298K) and one atmosphere (14.7 psia or 101.3 kPa), but may vary from location to location, and between gas sales contracts. 

Another very important technique for fundamental consideration of multicomponent systems is low energy ion scattering (LEIS) [Taglauer and Heiland, 1980 Brongersma et al., 2007]. This is a unique tool in surface analysis, since it provides the ability to define the atomic composition of the topmost surface layer under UHV conditions. The signal does not interfere with the subsurface atomic layers, and therefore the results of LEIS analysis represent exclusively the response from the outer surface. In LEIS, a surface is used as a target that scatters a noble gas ion beam (He, Ne, ... 

Figure 8.5 shows the LEIS spectra of ZnAl204 and ZnO as a characteristic example of a multicomponent system analyzed by this technique [Brongersma and Jacobs, 1994]. Since only the surface peaks of A1 and O were detected for ZnAl204, the Zn atoms must be located in the subsurface layers. The onset of the tail agrees between the spectra, indicating that Zn is present in the second and deeper layers. This example illustrates the strength of the LEIS technique, in that characteristic peaks from different elements can be used to selectively analyze the atomic composition of the topmost surface. In addition, the shape of the tails could provide information on the in-depth distribution of the elements. 

The replacement of vanadia-based catalysts in the reduction of NOx with ammonia is of interest due to the toxicity of vanadium. Tentative investigations on the use of noble metals in the NO + NH3 reaction have been nicely reviewed by Bosch and Janssen [85], More recently, Seker et al. [86] did not completely succeed on Pt/Al203 with a significant formation of N20 according to the temperature and the water composition. Moreover, 25 ppm S02 has a detrimental effect on the selectivity with selectivity towards the oxidation of NH3 into NO enhanced above 300°C. Supported copper-based catalysts have shown to exhibit excellent activity for NOx abatement. Recently Suarez et al and Blanco et al. [87,88] reported high performances of Cu0/Ni0-Al203 monolithic catalysts with NO/NOz = 1 at low temperature. Different oxidic copper species have been previously identified in those catalytic systems with Cu2+, copper aluminate and CuO species [89], Subsequent additions of Ni2+ in octahedral sites of subsurface layers induce a redistribution of Cu2+ with a surface copper enrichment. Such redistribution... 

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