Copper carbon deposition

Figure 4.16 Thick calcium carbonate deposits on condenser tube and copper transfer pipe. Note the stratification.

Chelants are particularly useful in maintaining very clean, deposit-free waterside conditions and can be employed in both FT and WT boilers. In practice, however, they are relatively indiscriminant in their reactions and under unsuitable conditions may seriously corrode carbon steel, copper, and copper alloy boiler components. Chelants also may react with any available oxygen under BW conditions and temperatures. 

Alloying the nickel of the anode to improve tolerance for fuel contaminants has been explored. Gold and copper alloying decreases the catalytic activity for carbon deposition, while dispersing the anode with a heavy transition metal catalyst like tungsten improves sulfur resistance. Furthermore, ceria cermets seem to have a higher sulfur tolerance than Ni-YSZ cermets [75],... 

The lead isotope ratios indicate an upper cmstal source for the lead and are consistent with mineralization at 800 Ma. Tracer isotopes in carbonates and chalcocite concentrates indicate that an external fluid altered the dolomitic unit changing its isotopic composition as well as deposited copper mineralisation. 

The carbon deposits from these reactions were examined with an electron microscope, and they appeared to grow in the form of threadlike filaments. In several other cases of filamentary growth, it was found that the deposit contained appreciable amounts of the catalyst material. For example, in the formation of cuprene by the reaction of acetylene on copper oxide, copper was found in the cuprene at appreciable distances from the oxide surface (34). Similarly, in the deposition of soot on firebrick, iron has been found in the carbon. These facts suggest that the formation of a filamentary deposit may require the superposition of a small amount of the catalyst material on some of the reaction product. This material could then be carried away from the surface as the filament grew. The superposition of catalyst on the reaction product could be accomplished by the rearrangement process. 

The materials known to be sensitive to such attack are primarily those presenting a relatively thin facade of a substance that reacts readily with dilute acids (especially sulfuric). These include zinc (galvanized steel), certain paints, unprotected carbon steel. Copper (bronze) and carbonate stones (marble, limestone, some sandstones) may be attacked by acids, but their "sensitivity" will depend on the stock thickness and the intended service life. In the case of outdoor sculpture, for example, works of permanent value will be "sensitive" to deposited acids. 

Since one of the issues raised in this paper is whether the objects seen in the TEM images are a proper representation of the structures present in solution, we will describe briefly sample preparation strategies. For solutions of micelles in hexane, a very volatile solvent, samples for TEM studies could be obtained by aspirating a dilute solution directly onto a carbon-coated copper grid. Most of the solvent likely evaporated as the sample was deposited on the substrate. Alternatively, the TEM substrate could be dipped briefly into a dilute solution of the micelles and allowed to dry. This method also worked for less volatile solvents like decane. For decane, we could also place a small drop (a few pi) of solution on the grid and then touch the edge of the droplet with a Kimwipe to remove excess solvent. For several samples these methods were compared, and we observed the same morphology. 

Fig. 2 shows how the aminoday -metal nanoparticle composites form clear transparent solutions in water. The solutions are pink and yellow for Au and Ag respectively and dark brown in the cases of both Pt and Pd. The reddish-brown colour observed for Au-clay nanoparticle composites immediately after the addition of NaBH4 changed to pink with time. The solutions exhibit characteristic piasmon bands for the Au- and Ag-day suspensions at 520 nm and 410 nm respectively as shown in Fig. 3. In the cases of Pt and Pd, the characteristic absorption band for the precursor s around 260 to 280 nm was absent thereby confirming the formation of Pt and Pd nanoparticles. 7,18 TEM images of the aminoday-metal nanoparticle composites deposited on a carbon coated copper grid are shown in Fig. 4. The histograms show the average particle sizes to be around 3.5 and 5 nm respectively in the cases of Au and Ag nanoparticles. We could see the layered arrangements in the cases of Pt and Pd with the interspacing of 1.5 nm commensurate with the bilayer arrangement of aminoclays (see top right inset of Fig. 4b).

A spot analysis, using a Kevex-ray unit on a scanning electron microscope was performed on a piece of the fabric remnant and a piece of the washing test specimen. These specimens were mounted on a copper stud and had a thin deposition layer of carbon deposited over them. The following results were obtained from the technician who devised and performed the tests. 

Cook et al. also reduced CO2 using in-situ deposited copper on glassy carbon electrodes [121] and on electrodes of the gas diffusion type consisting of copper... 

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