Anodized surfaces, Initial

Fig. 2. Smoothing by ECM. Specification of a machined anode profile over time where (H) is the cathode tool and (—) is (a) the initial irregular anode surface, and (b) the final anode surface (--------------------------------------) is successive anode profiles over time.

Similar oxidative cyclization reactions involving the direct oxidation of acyclic 1,3-dicarbonyl compounds have not been reported. However, the generation of radical intermediates by the direct oxidation of cyclic 1,3-dicarbonyl compounds at an anode surface has been reported. Yoshida and coworkers have shown that the anodic oxidation of cyclic 1,3-dicarbonyl compounds in the presence of olefin trapping groups gives rise to a net cycloaddition reaction (Scheme 10) [23]. These cycloaddition reactions proceeded by initial oxidation of the 1,3-dicarbonyl compound at the anode followed by a radical addition to the second olefin. Following a second oxidation reaction, the material then... 

Although cyclizations from the direct anodic oxidation of acyclic 1,3-dicarbonyl compounds have not been reported, the analogous mediated reactions have been studied [24]. Snider and McCarthy compared oxidative cyclization reactions using a stoichiometric amount of Mn(OAc)3 with oxidations using a catalytic amount of Mn(OAc)3 that was recycled at an anode surface (Scheme 11). In the best case, the anodic oxidation procedure led to a 59% yield of the desired bridged bicyclic product with the use of only 0.2 equivalents (10% of the theoretical amount needed) of Mn(OAc)3- Evidence that the reaction was initiated by the presence of the mediator was obtained by examining the electrolysis reaction without the added Mn(OAc)3. In this case, none of the cyclized product was obtained. For comparison, the oxidation using... 

To help understand the process of nanotube formation, FESEM images of the surface of the samples anodized at 20 V for different durations were taken and analyzed. At the start the anodization the initial oxide layer [111], formed due to interaction of the surface Ti ions with oxygen ions (0 ) in the electrolyte, can be seen uniformly spread across the surface. The overall reactions for anodic oxidation of titanium can be represented as... 

Initial bondability of anodized surfaces was tested in the lap shear configuration using numerous commercial epoxy adhesives. With one exception, all surfaces proved to be bondable and gave acceptable lap shear values. That exception was an anodized film formed... 

Akbulut et al." polymerised styrene by a direct electron transfer initiation carried out at the anodic peak potential of the monomer. These authors claimed the following mechanism involving styrene adsorbed on the anode surface ... 

Ho et al. used a packed-bed reactor and a series of 316 stainless steel fiber an-ode/cathode pairs to decompose cyanide-containing effluent [41]. The cyanide destruction process was enhanced by the presence of metal ions, which led the authors to treat a copper cyanide effluent. The cyanide concentration was decreased from an initial concentration of 1400ppm to less than 20 ppm within a 4-20 h time period at an energy consumption of 5 -13 kW h/kg CN. At a CN/Cu ratio of 4.6 most of the copper was deposited on the cathode while some was converted to the divalent form and deposited on the anode surface as an oxide. 

Initial attempts to use aluminum for automotive trim were unsuccessful due to the corrosion behavior of the metal. It is therefore anodized for automotive trim applications to provide a protective oxide surface which acts as a barrier coating for corrosion pro tec tion. > 2 Aluminum and its alloys are susceptible to pitting and crevice corrosion in chloride containing environments. The corrosion resistance of anodized aluminum is therefore highly dependent on the quality of the anodized surface and the absence of scratches and other damage sites. 

Once the initial layer of PPy is deposited, it becomes a reactant that determines the course of the remainder of the polymerization process. Polymerization occurs more readily (at a lower potential) on the already-deposited PPy than on the anode surface. This process of product becoming reactant continues until the reaction is stopped. A more detailed investigation of the polymerization process reveals the intricacies involved in producing these sophisticated dynamic structures. Thus, the overall process may be broken into several discrete steps, as shown in Figure 2.1 (details are available in Reference 4). 

Before the anode potential measurements, the anodes were initially conditioned by electrolysis (chemical conversion treatment) applying a 160 g/1 H2SO4 electrolyte at 40 C and a current density of 50 mA/cm for 24 h in order to prepare a Pb02 oxide layer at the anode surface. The distance between the anode and cathode in the chemical conversion treatment was 3 cm. After the chemical conversion treatment, the anode potential was measured in a 160 g/1 H2SO4 and 60 g/1 Zn electrolyte at a current density of 50 mA/cm for 1,0 h. The experiment temperature was 40° C and the anode-cathode distance was 3 cm. Another experiment with the same characteristics as above mentioned, but without Zn in the electrolyte and with no preliminary electrolysis, was performed for 20 days electrolysis time, the electrolyte being replaced every two days. The aluminum cathode used in the experiments had a surface area of... 

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