Energy disperse spectroscopy , metal deposition

Removal of deposits and corrosion products from internal surfaces revealed irregular metal loss. Additionally, surfaces in wasted areas showed patches of elemental copper (later confirmed by energy-dispersive spectroscopy) (Fig. 13.12). These denickelified areas were confined to regions showing metal loss. Microscopic analysis confirmed that dealloying, not just redeposition of copper onto the cupronickel from the acid bath used during deposit removal, had occurred. 

Chong et al. [742] have described a multielement analysis of multicomponent metallic electrode deposits, based on scanning electron microscopy with energy dispersive X-ray fluorescence detection, followed by dissolution and ICP-MS detection. Application of the method is described for determination of trace elements in seawater, including the above elements. These elements are simultaneously electrodeposited onto a niobium-wire working electrode at -1.40 V relative to an Ag/AgCl reference electrode, and subjected to energy dispersive X-ray fluorescence spectroscopy analysis. Internal standardisation... 

The Bi-promoted catalysts were prepared by consecutive deposition of Bi onto a commercial 5 wt% Pt/alumina (Engelhard E 7004, Pt dispersion 0.30 determined by TEM) [7]. The reduction of bismuth-nitrate was carried out in a dilute aqueous acidic solution O10"6 M, pH = 3-4) by hydrogen. The metal content of the catalysts was determined by inductive coupled plasma atomic emission spectroscopy (ICP-AES). Preferential deposition of Bi onto Pt particles has been confirmed by TEM, combined with energy dispersive X-ray analysis (EDX) [7]. Pb-, Sn- and Ag-promoted catalysts were prepared similarly. 

Figure 3.7 shows the perforated and pitted areas of the boiler tubes, respectively. The region near the pit, which is thinned due to corrosion, had shown the layers of deposits over the surface. The deposits, when analyzed by energy-dispersive X-ray spectroscopy (EDX), showed the presence of V, S, Al, Si, and O (Figure 3.8). Electron probe microanalysis (EPMA) showed that the deposits were rich in V compounds near the pit (Figure 3.9). Although floor-area tube temperature is normally between 300°C and 450°C, the deposit would increase the temperature due to poor heat transfer effect, which is sufficient to cause melting of the salt compounds in the deposit. Once these salts are in molten state, they would undergo fluxing reaction, destroying the protective layer, and consequently, the metal undergoes hot corrosion. The presence of V and S as noticed on pits...

The role of bacteria. In a recent study on the activity of benthic bacteria in Amazonian rivers (22), microbial biofilms were collected off of submerged plants and sediment, and subsequently analyzed with transmission electron microscopy (TEM), coupled with energy dispersion X-ray spectroscopy (EDS) and selected area electron difiraction (SAED). th TEM, it was observed that bacterial biomineralization involved a complex interaction between metals in solution with the reactive components of the cell. The anionically-charged cell wall and the encompassing layers provided special microenvironments for the deposition of iron and other soluble cationic species. Ferric iron, which exhibits unstable aqueous chemistries, was bound in significant amoimts, and previous studies indicate that... 

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