Surface profiling

The true area of contact is clearly much less than the apparent area. The former can be estimated directly from the resistance of two metals in contact. It may also be calculated if the statistical surface profiles are known from roughness measurements. As an example, the true area of contact. A, is about 0.01% of the apparent area in the case of two steel surfaces under a 10-kg load [4a]. 

By using a laser with less power and the beam spread over a larger area, it is possible to sample a surface. In this approach, after each laser shot, the laser is directed onto a new area of surface, a technique known as surface profiling (Figure 2.4c). At the low power used, only the top few nanometers of surface are removed, and the method is suited to investigate surface contamination. The normal surface yields characteristic ions but, where there are impurities on the surface, additional ions appear. 

Lasers can be used in either pulsed or continuous mode to desorb material from a sample, which can then be examined as such or mixed or dissolved in a matrix. The desorbed (ablated) material contains few or sometimes even no ions, and a second ionization step is frequently needed to improve the yield of ions. The most common methods of providing the second ionization use MALDI to give protonated molecular ions or a plasma torch to give atomic ions for isotope ratio measurement. By adjusting the laser s focus and power, laser desorption can be used for either depth or surface profiling. 

Some solid materials are very intractable to analysis by standard methods and cannot be easily vaporized or dissolved in common solvents. Glass, bone, dried paint, and archaeological samples are common examples. These materials would now be examined by laser ablation, a technique that produces an aerosol of particulate matter. The laser can be used in its defocused mode for surface profiling or in its focused mode for depth profiling. Interestingly, lasers can be used to vaporize even thermally labile materials through use of the matrix-assisted laser desorption ionization (MALDI) method variant. 

Dicylopentadiene Resins. Dicyclopentadiene (DCPD) can be used as a reactive component in polyester resins in two distinct reactions with maleic anhydride (7). The addition reaction of maleic anhydride in the presence of an equivalent of water produces a dicyclopentadiene acid maleate that can condense with ethylene or diethylene glycol to form low molecular weight, highly reactive resins. These resins, introduced commercially in 1980, have largely displaced OfXv o-phthahc resins in marine apphcations because of beneficial shrinkage properties that reduce surface profile. The inherent low viscosity of these polymers also allows for the use of high levels of fillers, such as alumina tfihydrate, to extend the resin-enhancing, fiame-retardant properties for apphcation in bathtub products (Table 4). 

A variety of thermosetting resins are used in SMC. Polyesters represent the most volume and are available in systems that provide low shrinkage and low surface profile by means of special additives. Class A automotive surface requirements have resulted in the development of sophisticated systems that commercially produce auto body panels that can be taken direcdy from the mold and processed through standard automotive painting systems, without additional surface finishing. Vinyl ester and epoxy resins (qv) are also used in SMC for more stmcturaHy demanding appHcations. 

This equation is cubic in hquid depth. Below a minimum value of Ejp there are no real positive roots above the minimum value there are two positive real roots. At this minimum value of Ejp the flow is critical that is, Fr = 1, V= V, and Ejp = (3/2)h. Near critical flow conditions, wave motion ana sudden depth changes called hydraulic jumps are hkely. Chow (Open Channel Hydraulics, McGraw-Hill, New York, 1959), discusses the numerous surface profile shapes which may exist in nommiform open channel flows. 

Examination of surface profiles in these pitted regions under a high-power microscope revealed jagged, undercut profiles free of deposits or corrosion products. This appearance is typical of cavitation damage. 

Anchor Pattern (Surface Profile)—the shape and amplitude of the profile of blast-cleaned or grooved steel, which influences the bond between metallic or paint films and the substrate. 

Surface Treatment—any suitable means of cleaning and treating a surface that produces a desired surface profile that has required coating characteristics. 

P. M. Duxbury, W. Selke. Surface profile evolution above roughening. Z Physik B 04 311-318, 1994 P. M. Duxbury, W. Selke. EquiUbration of crystal surfaces. Phys Rev B 52 17468-17479, 1995. 

Shrinkage on curing means that a high standard of visual cleanliness and an exceptionally coarse surface profile is required on blast-cleaned steel. Its main use is for tank linings. 

This is an effective treatment on eroded and weak surfaces but will not open up the sub-surface voids or pockets or provide a surface profile on dense concrete. 

Measure the surface profile of the freshly blast-cleaned surface and ensure that it is within specification. 

The oxidation rate of pure Fe in Oj has been shown to be affected by specimen shape and the original surface profile . For iron oxidising in Oj, 50 50 O2 + HjO and O2 + COj rough surfaces have been found to oxidise more slowly than smooth surfaces, since surface irregularities hinder the oxide flow . The oxide is unable to deform sufficiently to maintain intimate contact with the metal surface such that porous scales are formed . 

Fig. 8.60 Schematic diagrams showing common surface profiles produced during fatigue (a) coarse slip and crack initiation adjacent to grain boundaries (b) extrusions and intrusions (c) coarse slip within a persistent slip band (after Lynch Y...

Countersunk rivets or screws give a surface profile which is compatible with painting protuding bolts and rivets are very much more difficult to coat adequately. Welded joints can aid optimum shaping for painting. Butt joints are preferable to lap joints. 

The coatings produced by metal spraying have an unusual structure which is characteristic of the method of formation. They are composed of small particles usually not more than 0-01 mm in diameter which, having reached the surface in the molten condition, have splashed outwards and then solidified. Figure 12.27 (left) shows in section the irregular form of the flattened particles. In transverse section the surface profile is undulating (Fig. 12.27 (right)). 

Fig. 34—(a) Representative SEM micrograph, (b) surface profiles of the scratch tracks, and (c) the evolutions of normal load and friction force between the tip and the film of the DLC film deposited at -90 V bias. 

Fig. 39 —Surface profiles of disk substrates polished in different slurries (a) before polishing, (b) polished in the slurry Type I, (c) polished in the slurry Type II.

The etch rates were measured by a surface profiler and field emission scatming electron microscopy (FESEM), and the etch profile were observed by FESEM. In this study, a C /Ar gas chemistry was chosen to obtain high etch selectivity of Si film to niobium oxide mask since CI2 gas was known to be a good etch gas for Si films. The etch rate, etch selectivity and etch profile of niobium oxide nanopillars and Si films were explored by varying the CI2 concentration, coil RF power and dc bias voltage to substrate. 

Wang YX, Balbuena PB. 2005b. Potential energy surface profile of the oxygen reduction reaction on a Pt cluster Adsorption and decomposition of OOH and H2O2. J Chem Theory Comput 1 935-943. 

Sometimes it is necessary to apply two (or more) variants of sample preparation to get different measuring samples from only one test sample. This is the case if various problems have to be solved, e.g. determination of major- and ultra trace constituents, comparison of depth- and surface profiles, or analysis of inorganic and organic trace components in the same test sample. An example is shown in Fig. 2.10 where in a test sample of wine both inorganic and organic trace constituents have to be determined and, therefore, different measuring samples must be prepared. 

Calculations using oscillatory ion profiles have also been performed61 and give better surface profiles and work functions for liquid metals. Such oscillatory profiles are expected on the following... 

Fig. 7. Theoretical surface profiles of collapsing bubble near a boundary. Initially, the distance of the bubble s edge from the boundary was Rq/2. [After E. A. Neppiras (26).]...

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