Surface samples examined

A typical sample would have a surface area of the order 10 x 20 mm. The preparation of the surface for examination is the subject of an ASTM standard (ASTM E1078-97), and the objective is to ensure that the surface to be analysed has not been contaminated or altered prior to analysis. The techniques of surface analysis are sensitive to surface layers only a few atoms thick, so the degree of cleanliness required will be much greater than for other forms of analysis. Nothing must be allowed to touch the surface to be analysed. 

To look for small voids, SEM was used. For the cracked sample, a fracture surface was examined, while a cut surface of the good sample was studied. This test showed large differences between the two samples with the cracked part showing significant voids. Figure 43(a) shows an SEM micrograph for the good... 

Substrate Characterization. Test coupons and panels of 7075-T6 aluminum, an alloy used extensively for aircraft structures, were degreased In a commercial alkaline cleaning solution and rinsed In distilled, deionized water. The samples were then subjected to either a standard Forest Products Laboratories (FPL) treatment ( 0 or to a sulfuric acid anodization (SAA) process (10% H2SO4, v/v 15V 20 min), two methods used for surface preparation of aircraft structural components. The metal surfaces were examined by scanning transmission electron microscopy (STEM) In the SEM mode and by X-ray photoelectron spectroscopy (XPS). 

F NMR of Fluorine-Doped -Alumina. The samples studied 115) were high surface area aluminum oxides doped with fluorine by addition of aqueous HF to alumina and subsequent dehydration. A suflScient number of paramagnetic impurities were present in the samples to give relaxation times of the order of 0.01 second. The BET surface areas of most of the samples examined were within 20% of 250 meterVgram. 

In summary, the NMR data on the samples examined indicate that fluorine occupies the surface phase up to the order of 5 wt. % F, and forms a bulk phase of aluminum fluoride at higher concentrations of... 

Fracture surfaces were examined in an ISI, Inc. Super III-A SEM. Cold snap samples were fractured after being submerged in liquid nitrogen for ten minutes. Crack faces of the 3PB and CT specimens were also studied with SEM. 

The coarseness of a surface and consequently the effect of surface treatment can be measured with a laser beam. In addition the surface is often investigated by means of various microscopic techniques. The nature of a surface can tell us something of the structure of the material. The information obtained depends on the treatment the area has undergone and the way in which the surface is examined. The researcher may want to determine how many phases there are present in the sample, how they are distributed throughout the sample or what the pores and the pores distribution are like. For these purposes many kinds of light and electron micros-copes are available. 

Figure 2. Multiple bioassay examination of porewaters and elutriates of two sediment samples collected from the River Saar. The pT scale is based on a geometric dilution series with the factor 2. Bed surface sample AW 1 ( , ) and core sample AW 2 (, O), (Krebs, 1999).

Critical surface tensions of functional polymers were experimentally determined. This set of data and the data on elastomers obtained previously were used to elucidate the proposed solubility parameter-surface tension relationship and the proposed parachor-surface tension relationship. The results show that the former has a higher correlation coefficient than the latter. The correlation coefficients, including three highly hydrogen-bonded polymers, are 0.731 for the former and 0.299 for the latter. Otherwise, they are 0.762 for the former and 0.178 for the latter. For the size of samples examined, we can conclude that the proposed solubility parameter-relationship is more effective than the proposed parachor-relationship in calculating critical surface tension of a polymer. 

There is increasing evidence that pesticides have contaminated extensive areas of the world not directly treated with pesticides. In many instances, the translocation can be attributed to food or water as the transmission vehicle. Another medium of dispersal of pesticides is the atmosphere. Analyses of rainwater and dust have revealed the presence of chloro-organic substances in all samples examined. Identification of specific pesticides has demonstrated that at least some of the chloro-organic compounds are pesticidal in origin. An analysis of dust, whose distant origin was documented by meteorological evidence, proved that pesticide-laden dust can be transported over great distances via the atmosphere and can be deposited over land surfaces remote from the point of application. 

Figures 30.17-30.19 depict the durability of the surface treatments examined with ETA-3183, which is the most difficult one to modify the surface effectively among samples employed. Because the water can reach the interface directly through cross-cuts, this accelerated adhesion test was much more severe when cross-cuts were...

The extreme surface sensitivity of XPS may be a handicap under certain circumstances. It may also be interesting to examine the sub-surface sample composition. This is possible using an ion gun to erode the surface of the sample. As erosion rates arc of the order of a nm/min... 

This approach does, however, leave some gaps and is fairly tedious if the equipment needs recalibrating. Surface contamination of the compounds may also influence the result. This is not generally considered problematic in so far as the samples examined often themselves have a contamination layer the two effects partly compensate for each other. 

The femur was chosen for its cylindrical symmetry, which permitted soil sampling in a full 360° solid arc around the bone without significant contamination from the effects of neighboring bones from the same skeleton. Furthermore, we have shown (8) that the femur is less sensitive to diagenetic effects than the rib, for example. The femurs appeared to have decomposed more on the underside than on any other surface. Soil sample sets were not usually complete because most skeletal discoveries could not be anticipated. Burials were normally located in a pit that had been backfilled at the time of interment. Consequently, soil within and outside the pit need not be of the same materials. Vertical samples well below the skeleton and horizontal samples well away from the skeleton may reflect a change in the type of soil. With one exception, only burials that had been located on a level surface were examined in order to avoid the effects of soil creep (JO). 

The main characteristic of the SPM is a sharp probe tip that scans a sample surface. The tip must remain in very close proximity to the surface because the SPM uses near-field interactions between the tip and a sample surface for examination. This near-field characteristic eliminates the resolution limit associated with optical and electron microscopy as discussed in the previous chapters, because their resolution is limited by the far-field interactions between light or electron waves and specimens. Diffraction of light or electron waves associated with far-field interactions limit their resolution to wavelength scales. The near-field interactions in a SPM, however, enable us to obtain a true image of surface atoms. Images of atoms can be obtained by an SPM because it can accurately measure the surface atom profiles in the vertical and lateral directions. The lateral and vertical resolutions of an SPM can be better than 0.1 nm, particularly the vertical resolution. The lateral range of an SPM measurement is up to about 100 /xm, and its vertical range is up to about 10 /xm. However, the SPM must operate in a... 

The dissolved Cu showed strong positive correlation with dissolved and exchangeable Mn whereas Cu and Mn were independent of Fe concentrations. It can be concluded from this observation that the elements Cu and Mn were independent of the scavenging effects of Fe. Only 2.8 percent of Cu and 10.9 percent of Mn were associated with the oxide fraction of solid phase as compared to 5.35 percent of Cu and 14.49 percent of Mn which were found to be associated with the carbonate fraction of the solid phase(13). It has been reported that generally, in the surface layers of natural waters, the conditions of pH and oxygen are such that Mn - introduced into these layers is readily oxidized to insoluble MnOa (40). This apparently was not true for the surface waters at SRP. The average pH of water samples examined at... 

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