SEM and EDS analyses

For a quantitative analysis of the spectrum in Fig. 6. the following sequence of steps was taken  

The outcome of the analysis of the integrated peak intensities shown in Fig. 6 is shown in Table 1 after corrections for different photoelectron cross sections and for the different inelastic mean free paths for the photoelectrons. The C l.s peak was not included in the quantitative balance since it was felt to represent a contamination overlayer which was not an integral part of the corrosion film. Previous XPS intensity studies of reference oxides showed reasonably good agreement with expected stoichiometries [9]. From the analysis, it can be seen that this film contained more oxygen than was accountable by stoichiometry the balance is believed to be water of hydration. 

Depth profiling can be carried out in conjunction with XPS analysis. The procedure. however, is time consuming and what chemical information was present 

Identifying number Binding energy Relative area Assignment 

One noteworthy characteristic of XPS that is particularly useful to corrosion science is the relatively low degree of damage that is imparted to soft surface structures, containing hydrates or chemisorbed species. TTie flux of low-energy X-ray photons produced by all but the most recent XPS systems is sufficiently low that strongly hydrated structures appear to remain intact even after hours of exposure. Since some passivating corrosion films may contain hydrates, it is important to have a spectroscopic technique such as XPS which may provide future support for the role of water in such films. 

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SEM and EDS analyses confirmed that the presence of clay cement in the sandstone aggregates influenced the boundary between cement paste and aggregate. This would cause a significant effect on the strength of concrete. 

For SEM, XPS and EDS analyses, the samples were treated with a 10% formalin solution, then washed thoroughly with Millipore water, and finally dehydrated in a graded series of water-ethanol mixtures and subjected to vacuum drying at room temperature. 

As discussed by Rossen (2014) and Rossen et al. (2013), point analyses can be carried out on a few hundred points in only a few hours and give general information on the phases present. The optimal conditions should be determined for each combination of SEM and EDS detector because cement hydrates are highly susceptible to beam damage. General guidelines for the setup of the microscope include the following (Rossen 2014 Rossen et al. 2013) ... 

Brock, A. L., Buck, B., Johnson, W. Ulery, A. L. 2003. Corrosion of depleted uranium in an arid environment Characterizaion with XRD, SEM/ EDS, and microprobe analyses. Geological... 

Traces of unreacted silica (Si02) in the SiC will produce a fluffy white precipitate, about which little is known. Certainly it is known that when hot concentrated phosphoric acid is in contact with glass hardware, the rapid formation of a fluffy gelatinous white precipitate is seen. From an X-ray diffraction analysis of the precipitate from operating fuel-cells, it was determined that the principal component was Si3(P04)4, although metallographic and SEM/EDS analyses support the presence of the other silico-phosphate complexes in varying amounts. 

By compiling the information gained from the SEM, XRD, and ED AX analyses and comparing it with information in mineralogical texts (11,12), some conclusions can be drawn about the chemical composition of the black and green components of sides A and B (Table I). 

SEM/EDS analyses of all particles <1 mm differentiated microplastics, including multi-colored plastic spheres, from other materials such as coal ash. Based on dense urban populations adjacent to the lakes that employ combined sewage overflow, and the convergence of lake currents near our sample sites, we believe the microplastic spheres may be microbeads used in consumer product applications, such as those used in facial cleansers. 

The saturation states of these waters with respect to a range of minerals were calculated using the computer code PHREEQE. This approach indicated that the groundwaters are approximately in equilibrium with respect to quartz, calcite, kaolinite, fluorite, ferrosilite, ferric hydroxide and siderite (Table 2). The water/rock interactions deduced from the SEM-EDS analyses and the theoretical calculations using PHREEQE, are summarized in Table 3. 

SEM/EDS analyses were performed by using an EVO 50 Series Instrument (LEO ZEISS) equipped with both an INCAEnergy 350 EDS micro-analysis system and an INCASmartMap for imaging the spatial variation of elements in a sample (Oxford Instmments Analytical). The accelerating voltage was 25 kV, the beam current 1.5 nA, and the spectra collection time 100 s. X-ray diffraction (XRD) patterns were collected with CuKa radiation (X= 1.5418 A) by means of a X PertPro PANalytical... 

A good example of combining information from polished sections in the SEM is the study of the mechanism of sulfate attack made by Yu et al. (2013). Here EDS maps of Ca and S were used to determine sulfate and calcium profiles inside mortars immersed in sodium sulfate solutions. These were used to identify regions of interest, which were studied in detail by BSE images and carefully selected EDS analyses plotted in scatter plots. 

Figure 8.53 (a) EDS analyses from SEM and STEM compared for a white cement sample hydrated for 5 years (b) same comparison as (a) for a blend with 40% slag, hydrated for 5 years. 

The problem of intermixing in SEM is especially problematic in blends with SCMs of small particle size, e.g. silica fume and finely ground metakaolin. Estimation of the C-S-H composition from SEM-EDS analyses may be very difficult. STEM-EDS is therefore particularly useful to analyse areas of C-S-H devoid of very small unreacted or hydrated phases whose presence is visible in the STEM-BF image in Figure 8.54a of a cement-metakaolin blend hydrated for 90 days at 20°C. The elemental map (Figure 8.54b) confirms that metakaolin particles (MK) are still present in these images. In Figure 8.54c, the STEM-EDS analyses show where the composition of pure C-S-H is likely to be located compared to the SEM-EDS plots. Pure C-S-H is between analyses intermixed with MK and those intermixed with AFt or AFm. 

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