Anode, annealing treatment

Differences in metallurgical condition due to thermal or mechanical treatment. Cold worked areas anodic to annealed areas, metal subjected to external stress anodic to unstressed metal. 

Fig. 4 shows the SEM images of SWNTs purified by the thermal oxidation and acid-treated. Fig. 4(a) shows a SEM image of the raw soot. In addition to the bundle of SWNTs, carbonaceous particles are shown in the figure. These stractural features mi t be causal by various in the arcing process because of an inhomogeneous distribution of catalysts in the anodes [7]. It can be seen that the appearance of SWNTs was curled and quite different fiom that of MWNTs. Fig. 4(b) shows a decrease of amorphous carbons after oxidation. The basic idea of the selective etching is that amorphous carbons can be etched away more easily than SWNTs due to the faster oxidation reaction rate [2]. Since the CNTs are etched away at the same time, the yield is usually low. The transition metals can be etched away by an add treatment. Fig. 4(c) shows the SEM image of the acid-treated sample, where the annealed sample was immersed in 10 % HCl. 

Figure 43 illustrates the possible current transients during thermal treatment of Al-anodic Al203-Au structures at linearly increasing temperature (a) and during isothermal annealing (b). The first case is characterized by a TSC maximum at —400 K followed by a change in current direction and a second maximum (Fig. 43a). In the case of isothermal treatment, jTSC follows a t n dependence, where n is close to unity. These findings are usually interpreted in terms of a release from deep traps of those electrons that were initially captured there in the process of anodization. There are no clear ideas as to the physical nature of these traps. Parkhutik and Shershulskii249 have postulated that traps are associ-...

The negative resistance effect is observed when anodic oxides are subjected to so-called electroforming (i.e., annealing in vacuum).93 Such a treatment removes the special features of the anodic oxides (asymmetry of conduction and electric strength, electret effect, etc.), and the negative resistance effect may be explained using the general approach developed for amorphous dielectrics.5... 

The electrical properties of an anodic oxide are found to depend on the formation conditions and subsequent treatments such as annealing. As-prepared anodic oxides show high leakage currents and a diode-like behavior known from anodic oxides of valve metals. A short high-temperature anneal, which removes the bound hydroxyl, reduces the leakage current to values typical of thermal oxides, as shown in Fig. 5.9. 

In rare cases, a relatively small area near the weld will be an anode to the relatively large cathodic surface area of the parent metal. In moderately corrosive media, this zone may corrode much faster than either the weld metal or the parent metal. Postweld heat treatment is usually helpful. In some instances, normalizing (or even solution annealing in the case of an austenitic stainless steel) the weldment is necessary, a measure that can cause significant distortion problems. In most cases, the weld metal, HAZ, and parent metal do not have significant galvanic differences. 

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