Coating conductance interpretation

Other commonly employed redox electrodes are metals such as copper, cobalt, silver, zinc, nickel, and other transition metals. Some p-block metals such as tin, lead and indium can also function as redox electrodes. However, s-block metals such as magnesium do not make good redox electrodes since the elemental metal is reactive and forms a layer of oxide coating, which leads to poor reproducibility, poor electronic conductivity and electrode potentials that are difficult to interpret, (see Section 3.3.1). 

Samples of both fulvic and humic acids were suspended in methanol and methylated with diazomethane. Both H and spectra of the free acids were obtained, at 299.94 MHz and 75.42 MHz respectively, on a Varian XL-300 spectrometer having a Nicolet TT-100 PET accessory. Spectra were obtained in D2O, in a 12-mm tube, with deuterated TSP (sodium 3-(trimethylsilyl)propionate-, , 3,3- 4) added as internal reference. GC/MS of methylated acids was conducted on a Hewlett-Packard Model No 5995 GC/MS/DA system equipped with a fused silica capillary column (12 m x. 020 mm ID, Hewlett Packard) internally coated with crosslinked methylene silicone. Infrared spectra were obtained with solid samples dispersed in KBr pellets, by using a Beckman IR-33 spectrophotometer. The various absorption peaks in IR and NMR were interpreted conventionally (9-10). 

Despite some possible implementation problems and the need for sophisticated requirenwnts for interpretation, these measurements can prove particularly valuable in low conductivity media -such as concrete, soils, condensate corrosion, protection by coatings etc. They therefore provide a more accurate determination of R. ... 

For optical microscopy of fracture surfaces usually little or no surface preparation is necessary. However, because plastics have poor electrical conductivity, for SEM examinations the sample surface generally needs to be coated with a conductive layer that prevents charging and heating. The energy carried into the sample can melt the polymer or vaporize low molecular contents locally and change the fracture surface irreversibly, making its interpretation impossible. On the other hand, to ensure artifact-free imaging, the applied layer itself must not have any visible structure and must be so thin that the structures on the surface are not hidden. 

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